Source: Apple

The release of Apple's (NASDAQ:AAPL) iPhone 6 is sure to be the marquee storyline of the fall, possibly even for all of 2014, for technology enthusiasts.

The upcoming iPhone 6 will mark Apple's most important device release in more than two years for a number of reasons, and the market certainly appears to have noticed.

And while the final details for the upcoming Apple iPhone 6 remains somewhat vague, here are three key ways to look at the iPhone 6 for tech enthusiasts and investors in the run-up to its eventual launch.

1) What we know made it in
With the iPhone 5s and 5c, Apple segmented its smartphone lineup by cost. And with the iPhone 6, Apple will further divide its iPhone lineup by screen size. Splitting the iPhone 6 in 4.7-inch and 5.5-inch models will serve as the most defining aspect of the new iPhone. This move has been confirmed by a number of reputable sources, meaning it's about as sure a change as investors can predict in predicting Apple's product innovations. However, it by no means the only virtually sure-fire detail that's emerged for the iPhone 6 either.

In terms of internal components, Apple's widely anticipated A8 chip will receive a serious speed upgrade, jumping from 1.3 GHz per core in the current A7 to 2.0 GHz per core in the A8. As has been expected, Apple could once again tap Broadcom for an upgraded Wi-Fi chip, this one utilizing the faster 802.11ac standard. Similarly, Apple will use Qualcomm's advanced MDM9x35 as the cellular modem for the iPhone 6 and Apple appears to be incorporating a NXP Semiconductor near field communication (NFC) chip as well. Again, these aren't necessarily set in stone, but moves that have been reported from highly regarded sources. I think of them as "safe bets" so to speak.

2) What's less clear
Moving further down the certainty scale are a series of rumors that clearly make sense for the iPhone 6, but lack some aspect (specificity, multiple high quality reports, etc.) to make them truly features of upgrades worth betting on.

A great example of this kind of rumor is the on-going debate regarding the iPhone 6's screen material. Apple's continued interest in sapphire glass via its exclusive partner GT Advanced Technologies has spurred a litany of rumors. Some theorize Apple will make the entire iPhone 6's outer casing from the ultra hard material, although this seems extremely unlikely due to problems with producing sapphire en masse. Other rumors claim Apple could use an extremely thin layer of sapphire spayed atop the main screen material that would prove nearly as durable as an all-sapphire covering. Yet others argue the iPhone 6 will use an updated, and presumably more scratch-resistant, version of Corning's Gorilla Glass. So while it's probably too ambiguous to pin down the exact make and model that will cover the iPhone 6's screen, there's clearly a unified theme here -- the iPhone 6's screen will be new, improved, and extremely scratch-resistant.  

Other plausible but more difficult-to-confirm rumors include Apple overhauling the iPhone 6's camera and/or flash system, potential new innovations with the fingerprint scanning home button, and that chronic production problems delay the actual shipping date for the larger 5.5-inch iPhone 6. Again, each of these rumors, and many like them, seem eminently possible. However, in the absence of repeat mentions from high quality sources, it's hard to get too worked up over many of these details. Rather, we'll simply need to wait until the iPhone 6's likely launch on Sept. 9 (another likely rumor in and of itself).

3) A winner regardless
Either way, the Apple iPhone 6 is a virtual lock to be a massive commercial success for a host of reasons.

I've repeatedly discussed Apple's veritably gray-haired iPhone lineup in key markets like the U.S. and China. This fact alone should help make the iPhone 6 Apple's most successful device ever from a financial perspective. Potential sales estimates vary widely, and this article's been all about not listening to rumors, so I won't traffic in such matters here.

Ultimately though, this is the most important takeaway in setting your expectations for Apple's iPhone 6. It will be an absolutely massive commercial and financial success for the world's largest publicly traded company. So while the rest of the rumor mill will spend the coming weeks hemming and hawing over potential specs and features, I'll contend that this is really the only point worth truly considering.

[Editor's note: Corrected the iPhone 6 Apple error to the iPhone 6]