In a previous column, I went over some of the technologies that I expect to see in Apple's (NASDAQ:AAPL) 2018 iPhone lineup, which I'll refer to as the iPhone 9 series.

Those predictions were relatively straightforward to make since they were largely based on knowledge of publicly announced technologies from known Apple suppliers, as well as an announcement from a longtime Apple supplier about its technologies not being included in future Apple chips.

Three Apple iPhones showing different aspects of the Apple App Store.

Image source: Apple.

In this column, I'd like to talk about two potential areas of improvement that Apple could bring to the iPhone 9 series that aren't so straightforward (or, frankly, as "guaranteed" as the ones I wrote about previously).

Next-generation 3D Touch

In the fall of 2015, Apple introduced its iPhone 6s series of smartphones. These phones disappointed in the marketplace, as iPhone shipments dropped year over year during the iPhone 6s product cycle, but with this line of devices, Apple introduced a feature marketed as 3D Touch.

3D Touch allows the device to respond to varying degrees of pressure that the user applies to the display and has been increasingly integrated into iOS, as well as the third-party app ecosystem over the last couple of years.

Apple didn't change how 3D Touch behaves with the iPhone 7-series devices, and the generally active rumor mill doesn't seem to point to any big changes to 3D Touch functionality in this year's iPhone models, either.

Next year, however, Apple could introduce a next-generation 3D Touch capability. There were rumors going around ahead of the iPhone 7 launch that Apple was testing a "multi-3D Touch" technology, but obviously that feature didn't happen last year, nor is it likely to come this year.

But, I think it's a possibility for the 2018 iPhone models, particularly as 3D Touch capability seems to be one of the key differentiating technologies for Apple's iPhones relative to other flagship smartphones -- evolving it seems only natural.

Voice biometrics

This year, Apple's OLED iPhone isn't expected to include the company's Touch ID fingerprint authentication technology. In place of Touch ID, Apple is expected to include facial recognition technology, which Bloomberg's Mark Gurman says should be quicker than Touch ID.

Though facial recognition sounds like it could be quite good, Apple seems to take the security of its devices seriously, and as such, I'd expect the company to always be on the lookout for ways to enhance the security features of its devices.

One thing Apple could implement is voice biometrics (which could be marketed as "Voice ID" or maybe "Siri ID"). You may recall that longtime Apple audio chip supplier Cirrus Logic (NASDAQ:CRUS) recently talked about "taping out" (that is, completing the design of) a so-called voice biometric chip, with sampling of the chip to customers beginning in the fall.

Clearly, if Cirrus Logic will be sampling the chip this fall, it's not going to make it into this year's iPhone models. However, if the technology proves compelling enough, I wouldn't be terribly surprised to see Apple adopt the chip (or some customized variant specifically for Apple) in the 2018 iPhone models.

Apple could also conceivably wait for a future iteration of the chip and deploy the technology in its 2019 iPhone models.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.