As the newest iPhone’s announcement draws near, the anticipated handset’s further physical evolution has been a point of near-ceaseless speculation. With the latest round of rumors about the mobile’s aesthetic future, two things stand out above all others. There’s the wholly expected expanded screen, assumed to end up somewhere between 3.7 and four inches in diagonal size. However, that screen’s promoted partner element — a redesigned, horizontally-elongated home button — represents a significantly more questionable reality.

As we’re all aware, Apple — perhaps more than any other company in the consumer tech sector — is extremely aggressive in protecting the specifically recognizable physical features of its many wares. This so-called “trade dress” is especially important to the Cupertino company because each entry in its library of devices is engineered with as much emphasis on external form as internal harmony. And, for the brand’s globally-recognized mobile lineup, there are only two unified design elements that, for these last several years, say “Apple” more than anything else.

One of these elements, the proprietary 30-pin charging/synching cable, has been a solid moneymaker for Apple for ages. Of course, most folks don’t pay a whole lot of attention to such an accessory (essential though it may be). Rather, it’s the aforesaid home button that sits front and center, both literally on every iDevice and in the figurative eye of the international public.

That simple, circular, square-sporting toggle is the preeminent physical component of any (and every) piece of iOS kit. In other words, it’s the most iconic feature across an increasingly iconic family of mobile hardware.

The notion that Apple is considering a dramatic alteration of the home key is interesting but worrisome; and, while it’s easy to see that various case mockups indicate an ovular insert could replace the classic disc, potential reasons behind the change aren’t as easy to pinpoint.

Oh, no, say it ain't so...

Initially, we bloggers were given to understand that Apple’s next-generation iPhone would retain its dimensional form factor even as it increased usable display real-estate. Obviously, this approach would require near-total bezel elimination on the iPhone’s left and right sides. Additionally, the screen would have to encroach on its vertical frames by as much as 50 percent. As such, there’d be less room on the bottom of the handset to accommodate the traditional home button, and — to keep things from being too proportionally skewed — an elongated button could be reasonably called for. It wouldn’t be pretty, but it would serve a purpose.

However, it doesn’t appear Apple is interested in keeping the new iPhone’s housing congruent with last year’s model. All the leaked renders so far seem to indicate a larger device has been built to accommodate the larger screen. If Apple then intends to keep the new display within the parameters discussed above, there should be ample space for a proper home key down below. Naturally, there is the possibility that those infinitely loopy engineers have figured a way to up the screen’s size even beyond our expectations, but — considering global supply constraints and capacities — it would be difficult to do so while maintaining the commercial spirit of the “Retina” moniker and cross-device aspect ratio compatibilities. Still, it seems logical that, if Apple were willing to enlarge the entire iPhone, the company would make it big enough to keep its most recognizable feature intact.

From a technical standpoint, there doesn’t appear to be any specific benefit to the wider clicker. Some commentary has focused on the possibility that Apple could use the expanded space as a sort of webOS-like gesture area, but no supporting code in the many developer iterations of iOS 5 support the notion. And, frankly, a capacitive, sub-screen, depressible swiping surface goes against the fundamental grain of iOS’ lauded simplicity.

From a usability and ergonomic standpoint, too, the key is… off. True, the full pad of a human thumb is somewhat oval-shaped, but a user doesn’t generally splay the entirety of his digit across the home button to engage it. In most scenarios, the key is used as intended, pressed down with a quick jab of the (much more) circular thumb tip. Also, the key is slightly concave, serving to draw a given press — even sight unseen — directly into the center of the mechanism. Since the home toggle is actually one of the most common points of failure on an iDevice, it’s hard to imagine the purported future version would hold up well spreading pressure around the longer sides of the switch (instead of consistently atop it). For example, my iPhone 4′s home toggle is almost completely unresponsive, and — unless I press down deliberately and precisely dead center — the action will not register. This problem would only be exacerbated if the replacement rumors turn out to be true.

I, for one, believe that they aren’t. And perhaps Case-Mate’s recent reluctance to show the front sides of its upcoming iPhone 5 wardrobe is indicative that the mainstream accessory-maker remains equally unconvinced of the likelihood of that lengthened button.

It is, after all, quite the stretch.

QUITE the stretch.