The current iPhone 5s measures four inches diagonally. But that could change very soon. Source: Apple.

Apple's (NASDAQ:AAPL) investors and consumers have been looking for a bigger iPhone for a while now. Samsung dominates the large-phone category and offers a wide variety of device sizes, but Apple has been conservative, increasing its phone to just four inches when it launched the iPhone 5 last year.

But recent documents shared in a trial between Apple and Samsung show Apple knows how important a larger iPhone 6 could be in light of the competition.

"Consumers want what we don't have"
In slides obtained by Re/code, Apple showed fiscal 2014 data that points to an overall trend toward bigger phones, as well as devices that cost less than $300. A very blunt slide labeled "Consumers want what we don't have" showed that smartphone buyers are looking for devices with screens that are larger than four inches, and that the majority of growth was happening with devices cheaper than $300.

Smartphone growth is trending away from the iPhone's price and size. Source: Scribd via Re/code.

Further slides show that Apple, not surprisingly, knows consumers are looking for smartphones that are bigger and less expensive than its iPhone.

Apple knows consumers are looking for something more. Source: Scribd via Re/code.

While it's unusual to see Apple so honest about where it stands among the competition, the slides aren't all that revealing. Data from International Data Corporation shows the smartphone market grew by 38% in 2013, but Apple's growth was just 13%. But now we have actual confirmation that Apple knows what many consumers already know: The iPhone is expensive and it has a smaller screen than a lot of other devices.

Great. Now what?
Getting a glimpse into Apple's mind is good, but how does this help investors? For one, it means Apple no longer has an excuse not to release a larger screen for the iPhone 6. In fact, now that we all officially know a little insight into Apple's knowledge of consumer preferences, it would be pretty irresponsible for them not release a larger device. 

I'm trying to imagine the iPhone 6 debuting this fall and Apple revealing a brand-new high-end spec device with a four-inch screen, and then everyone's jaw drops because the device has a been-there-done-that feel to it. With all the articles surrounding a larger screen size, or two, and now these documents surfacing I can't see how the current screen size could possibly stick around for the iPhone 6.

OK, so let's (safely?) assume the iPhone 6 has a bigger screen and is released in early fall of this year. Brian Marshall, an analyst at ISI Group, thinks there's a lot of large-screen iPhone demand pent up among consumers, and I agree. Marshall said in an investor note, acquired by Apple Insider, that the demand could translate into a 14% upgrade rate for the iPhone 6, among current iPhone users. According to his calculations, typical upgrade percentages among iPhone users are about 9% in an average quarter.

Whether Marshall's predictions prove true, I still think the pent-up demand theory is very plausible. Loyal iPhone users, of which there are many, will likely be offered the largest iPhone to date some time this year, and for many it'll be a hard offer to pass up.