So far, I’m betting on an A5X-powered Retina iPad Mini by this fall. While I’m making semi-crazy predictions about future iOS products so I can look back on this in a year and probably feel like an idiot for being so wrong, here’s one more.

The recently rumored, larger-screened “iPhone Math”, or more likely “iPhone Plus”, is plausible as an additional model (not a replacement) alongside the 4” iPhone. And there’s a good chance that it would have a 4.94”, 16:9 screen.

The theory is easy to understand: perform John Gruber’s Mini-predicting math backwards. The iPad Mini uses iPhone 3GS-density screens at iPad resolution. What if an iPhone Plus used Retina iPad screens with iPhone 5 resolution, keeping the rest of the design sized like an iPhone 5?

Marco Arment on the “iPhone Math” or “iPhone Plus”.

I’m still not convinced, because there’s so much practical advantage to the one-handed nature of the current iPhone screen size(s). The iPhone 5’s taller form factor made more sense to me. Still, Marco does make a good case, much in the same way John Gruber did for the iPad mini. I still just don’t see the point of making something bigger for its own sake. If someone can present the business case for a 5″ iPhone beyond “everybody else is doing it,” that would really give me some incentive to buy into it.