We keep hearing that the big global automakers are gearing up to challenge Tesla (TSLA -3.55%) with premium electric vehicles of their own. We've already seen one, the impressive Jaguar I-Pace crossover.

But what are the others? And when will they arrive?

Below you'll find the roadmap, a handy-dandy guide to when we can expect the long-talked-about Tesla challengers, upscale battery-electric vehicles from established automakers, to actually arrive at dealers.

2018: Jaguar and (maybe) an Audi SUV

First up is the I-Pace, the crossover SUV from Tata Motors' (TTM) Jaguar luxury brand. The I-Pace has already begun shipping in Europe, but it won't arrive in the United States until the second half of 2018.

A red Jaguar I-Pace, a sporty midsize SUV, on an oceanfront road.

Jaguar's electric I-Pace is the first car from a global automaker to challenge Tesla directly. Image source: Jaguar Land Rover.

If you follow electric vehicle news, you probably know all about the I-Pace. But just in case, here's a quick summary: dual motors, all-wheel-drive, a 90 kilowatt-hour (kWh) battery giving 240 miles of range, 0 to 60 miles per hour in 4.5 seconds, starting price of $69,500.

Also coming soon, but not quite that soon: An electric SUV from Audi AG based on a concept vehicle that Audi first showed in 2015. Audi has been referring to it as the "e-tron quattro," though it may get another name before production. Audi promises around 280 miles of range from a 95-kWh battery pack driving a three-motor system -- one motor in front, two in back.

The e-tron quattro prototype, a sleek midsize SUV covered in black and white camouflage, parked on a lakefront.

The Audi e-tron quattro prototype, a pre-production version of an all-new battery-electric Audi SUV coming late in 2018. Image source: Audi AG.

Whatever Audi calls its handsome electric SUV, it's expected to begin arriving at European dealers at the very end of this year, and at U.S. dealers in the first half of 2019. Audi said its price in Europe will start at 80,000 euros (about $93,000). U.S. pricing isn't yet known, but it'll be in that ballpark.

2019: Mercedes-Benz joins the premium-EV fray

Daimler AG (MBGA.F -0.21%) has a slew of electric-vehicle initiatives under way, including an all-electric Class 8 (tractor-trailer) truck for its Freightliner brand that will take on Tesla's Semi.

The Mercedes-Benz EQA, a compact electric SUV, shown wrapped in black and white camouflage and parked next to a field.

A pre-production Mercedes-Benz EQA, an all-electric SUV that will go into production in 2019. Image source: Daimler AG.

Naturally, Mercedes-Benz also figures prominently in its plans. Mercedes is expected to launch its first premium long-range electric vehicle, the EQC, in 2019. The EQC is a five-passenger SUV with two motors and a 70 kWh battery pack that is expected to give it around 250 miles of EPA-rated range. Mercedes promises a 0 to 62 miles per hour time of under five seconds, putting it in the same ballpark as the Audi and the Jaguar (and the base versions of Tesla's Model X).

The introduction of the second premium electric Audi, called (again, for now) the e-tron Sportback, will also happen in 2019. Its specs are similar to those of the e-tron quattro, but the shape is different: It's sort of a cross between an SUV and a sleek coupe-like sedan. One can envision it taking sales from Tesla's Model S, assuming that the price and performance are competitive.

The Audi e-tron Sportback, a battery-electric SUV with a low-slung, coupe-like roofline, shown parked near a lake.

Audi's e-tron Sportback Concept previews another electric Audi, this one due in 2019. Image source: Audi AG.

Possibly arriving in 2019: The long-awaited electric Porsche. Known as the Mission E in concept form, Porsche said earlier this month that its first-ever electric production car will be known as the Taycan (TIE-can).

The Taycan will bring a slew of innovations, including an 800-volt drive system that will allow for super-fast recharging (about 15 minutes to an 80% charge). Porsche promises all-wheel drive, a 0 to 62 miles per hour time of "under 3.5 seconds," and a battery system that will allow for repeated full-power acceleration runs, something that the fastest Teslas struggle with.

A black preproduction Porsche Taycan, an electric sports sedan, shown from the front on a test track.

A preproduction version of the Porsche Taycan, shown on Porsche's test track in Weissach, Germany. Image source: Dr. Ing. h. c. F. Porsche AG.

Two things we don't yet know for sure: When it will arrive, and what it will cost. I expect Porsche to offer several trim levels, with power and performance rising along with price -- likely from around $85,000 to around $150,000. As for when, late 2019 or early 2020 seem to be the best guesses at the moment.

Also possibly in 2019: The next electric Jaguar is expected to be an all-new version of the big XJ sedan. Jaguar hasn't yet announced it -- that's expected by the end of 2018 -- but it's believed to be fairly far along in development. Jaguar has already announced a major investment to reconfigure one of its U.K. factories to build electric vehicles, with the work expected to start early in 2019.

It's not out of the question that the first examples of this new electric Jaguar sedan could ship by the end of next year, but 2020 may be more realistic.

2020: BMW jumps in, and the next Tesla arrives

The picture gets fuzzier in 2020. We know that BMW AG (BAMXF -0.19%) will launch an electric version of its huge-selling X3 crossover in 2020, and that Tesla has said its Model Y -- a compact crossover based on the Model 3 -- could arrive in that year.

A "teaser" photo of a silver Tesla Model Y, a sleek SUV, viewed from the front.

Tesla's next mass-market vehicle will be the Model Y, a crossover based on the Model 3's architecture. It could arrive in 2020. Image source: Tesla, Inc.

Beyond that, we don't know yet. Mercedes-Benz is known to be working on at least two more electric vehicles -- a small premium car called the EQA, and an electric version of its big (and expensive) S-Class sedan, which might be called the EQS and is expected in 2020.

It's possible that we'll see an electric Cadillac by 2020, too. General Motors (GM -0.05%) is planning a slew of electric vehicles to be based on an all-new architecture expected in about 2021, but it has also said that there will be two new electric vehicles launched before then. Those two will share the electric-drive system developed for the current Chevrolet Bolt EV. One is expected to be a small Buick crossover, which wouldn't quite compete with Tesla -- but there have been hints that the other could be a Cadillac, which might.

Last but not least, Daimler is reportedly working on a big all-electric luxury sedan, which will probably take the name EQS when it arrives -- possibly in 2020.

The takeaway: Tesla's competition is finally arriving

Can Tesla compete directly with the big global automakers? That's the question Tesla skeptics have been asking for years. We're finally starting to find out: Early reviews of the I-Pace have been very positive with at least some reviews saying that the Jaguar is a step ahead of Tesla in some important ways.

We'll soon have several more points of comparison. Will Tesla prevail, or will the Silicon Valley upstart have to up its game? We'll know in a year or two.