Though Apple (NASDAQ:AAPL) has yet to formally unveil its next-generation iPhone models, most of the new features that'll be in this year's models have already been leaked out via generally reliable sources and publications.

This year's iPhones should help drive Apple's iPhone business to new heights in terms of both revenue and raw unit shipments -- something that Apple's iPhone 6s-series and 7-series smartphones launched in 2015 and 2016, respectively, failed to do.

Apple's iPhone 6 lineup in Silver, Gray, and Gold.

Image source: Apple.

However, Apple faces the very real challenge of trying to deliver iPhone unit and revenue growth in the coming years after what could be a blockbuster product cycle. That means the innovation engine can't slow down.

Next year, Apple is expected to launch at least two new flagship iPhone models -- one with a 5.8-inch OLED display like this year's premium model will have, and one with a jumbo 6.46-inch display.

Here's one way that Apple could make that 6.46-inch model truly stunning.

How about a curved display?

One thing that I'd like to see on future iPhone models is a curved display. Curved displays certainly make a device look sleek, and they allow a smartphone vendor to stuff a large display into a smaller footprint.

The Samsung (NASDAQOTH:SSNLF) Galaxy S8, S8+, and Note8 all employ curved displays to great effect.

Per market research firm TrendForce, which has been reliable in the past, Apple "will not implement the curved display design for the high-end iPhone because there are issues with the 3D glass in terms of production yield and drop test results."

Though the technology may not have been ready for Apple to deploy in this year's 5.8-inch premium iPhone, an additional year of development could allow Apple and its suppliers to overcome both issues.

Now, in an ideal scenario, Apple would employ curved 3D glass displays on both iPhone 9 models, but if deploying the technology that broadly just isn't feasible, it would make sense for Apple to endow the larger, more expensive iPhone 9 model with the technology.

This would make sense for two reasons. First, a curved display would allow Apple to reduce the physical footprint of the 6.46-inch model to the point where it'd still be a viable option for a relatively large swath of the smartphone-buying population.

Secondly, the technology would be limited to a more expensive/lower-volume device, which would allow Apple to achieve its desired gross profit margin percentage on sales of devices with what would surely be more expensive/difficult to make curved displays. The higher price point would also naturally reduce demand levels to something that Apple could have a chance of meeting.

Ashraf Eassa has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Apple. The Motley Fool has a disclosure policy.