Owners of VW and Audi models powered by the 2.0 liter TDI diesel engine may be eligible for a buyback soon. Image source: Volkswagen

Volkswagen (VWAGY -0.47%) has reached a "settlement in principle" with Federal and California regulators to resolve some of the issues around cars programmed to cheat on emissions tests, a federal judge said on Thursday.

We don't yet know all the details, and it may be a while before we do: The judge imposed a gag order on the parties while they work toward a concrete proposal that will be unveiled for public comment in June.

But here's what do know about the general shape of the deal.

A massive buyback, some payments to owners, and an environmental fund
According to a report by Reuters' David Shepardson, VW will offer to buy back almost 500,000 diesel-powered cars equipped with the software that evaded emissions testing. The cars eligible for the buyback will include 2009 and newer versions of the VW Golf, Jetta, and Beetle and Audi A3 equipped with the 2.0 liter four-cylinder "TDI" diesel engine. (The buyback apparently does not include Audi and Porsche models equipped with a 3.0 liter V6 diesel engine that was also implicated in the scandal.)

It's not clear how much money VW will offer to owners to buy back the cars. Judge Charles Breyer said that the deal includes "substantial compensation," suggesting that there will be a premium above book value. He also said that those with leased cars will be able to cancel the leases.

Owners will also have the choice of keeping their cars and having them repaired by VW. Reuters reported that VW has agreed to a compensation fund for owners that could represent $1 billion or more on top of whatever VW has to pay to repurchase vehicles. That suggests all owners may be eligible for some level of compensation, whether or not they choose to sell their cars back to Volkswagen.

It's expected that owners will have two years to decide whether to keep their cars or take the buyback offer. It's not clear whether VW will be able to repair and resell the cars it buys back, or whether it will be required to destroy them.

The final settlement deal is also expected to include an environmental remediation fund that addresses the excess pollution emitted by the cheating cars since 2009. It's not yet clear how big that fund will be, or how it will work.

So what is this going to cost?
It's impossible to say for sure until we have a lot more detail. But we can now make some semi-educated guesses.

Kelley Blue Book estimates that if all of the "generation 1 and 2" 2.0 liter vehicles are bought back at Blue Book Private Party values as of Sept. 24, 2015 (when the scandal first broke), the total cost would be $6 billion. If later "generation 3" vehicles, made in 2015, are included, then that total rises to $7.3 billion.

Add in that additional $1 billion to compensate owners, and assume $2 billion for the environmental remediation fund, and VW is looking at a bit over $10 billion if all of the owners of 2.0 liter-powered cars take up the buyback offer.

That's a hefty sum. But it may only be part of the story.

Even $10 billion may not be enough to resolve all of the complaints against VW
But even a $10 billion hit may may not resolve all of the complaints against VW here in the U.S.. Reports on Thursday suggested that the Federal Trade Commission may be willing to resolve its suit against VW for deceptive advertising as part of this deal. And it appears that attorneys for owners suing VW are signing on to this settlement as well. But it's not clear whether the settlement will include some resolution to the criminal investigations under way by the U.S. Justice Department.

And of course, this won't settle VW's (many) problems outside of the United States. But it's a start, and it gave VW shares a lift on Thursday. But for shareholders -- and owners of affected VW and Audi cars -- looking for specific answers, it looks like you'll have to wait a while longer.