Apple's (NASDAQ:AAPL) latest iPhone 6s and 6s Plus phones have finally been announced, with availability set to begin on Sept. 25. The new phones bring a whole bevy of improvements, ranging from the crazy-fast A9 processor to the inclusion of the new 3D Touch feature. Frankly, the improvements that Apple has delivered generation over generation in going from the iPhone 6 to the 6s are quite impressive.

However, the good news for Apple is that the iPhone 6s isn't perfect, meaning that the company likely has some very cool stuff in store for iPhone buyers next year. Here are three major improvements that I expect Apple to deliver with the next-generation iPhone, which will likely be called the iPhone 7.

Making it thinner and lighter
Apple's thing is that its latest phones are often thinner and lighter than the previous generation devices. Although the iPhone 6/6 Plus weren't lighter than the iPhone 5s -- because the displays were made much larger -- they were, at the very least, thinner. With the iPhone 6s/6s Plus, Apple made the devices slightly thicker and heavier than the preceding models.

Interestingly enough, according to well-respected analyst Ming-Chi Kuo, Apple is planning to make the iPhone 7 family of phones much thinner than either the 6 or 6s families. Although Kuo didn't comment on the potential weight of the next-generation iPhone, I suspect that next year's iPhone will be lighter, too.

An improved display
Though Apple included Force Touch in the 6s, the actual displays appear to be identical to the ones used in the iPhone 6/6 Plus. Apple generally makes large advances in display quality every other year, which is how the company is able to use the same displays for two years while still remaining competitive.

I suspect that, with the iPhone 7/7 Plus, Apple will, yet again, make a large leap in display performance relative to the 6/6 Plus and the 6s/6s Plus models. I expect improvements along the usual quality vectors such as contrast ratios, brightness, black levels, and color accuracy.

I'm also tempted to think that Apple will also increase the resolutions of its displays, although I'm not sure if the increased resolution and sharpness will really be worth the added power/battery drain associated with higher-resolution panels. 

Better cameras
With the iPhone 6s and 6s Plus, Apple made some big improvements in the camera subsystems of the phones relative to the iPhone 6 and 6 Plus, respectively. The rear-facing camera saw a resolution increase from eight megapixels to 12 megapixels, and the front-facing camera saw a big resolution bump from a mere 1.2 megapixels to five megapixels.

With the iPhone 7, I don't expect Apple to, yet again, boost the resolution of the cameras. Instead, I'm expecting an improved sensor, better low-light performance -- some reviews noted a slight regression in the 6s from the 6 in this area -- and a more sophisticated image signal processor integrated into the applications processor.

There's still plenty of innovation left in the iPhone
I think that the iPhone 6s is an incredibly compelling offering from Apple, and I expect that it should do quite well in the marketplace during the next year. However, taking a longer-term view, there's still plenty of things that Apple can improve upon in future iPhones.

This is a good thing because, as long as Apple can keep making better devices with significant and compelling new features and functionality, the company's iPhone business should continue to generate robust profits for years to come.

Ashraf Eassa has no position in any stocks mentioned. The Motley Fool owns and recommends Apple. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.