I'm kind of doubtful Apple would go to the 12/14/16 size scheme for the MBP, but if they did I'd order the 16" first minute its available.
Maybe its me and that I find the 13" an ideal size for a small notebook, and the 12" much less so.
I'm a developer, so even when I'm mobile, I'm looking at code all day and need as much screen real estate as possible. It's not unusual for me to have two pages of code side-by-side on my screen.
13" is a little small for my daily usage.
15" is just right.
17" is a ridiculous monster that I can't see ever carrying around.
That said, if I traveled by air on a regular basis and didn't need the screen real estate for coding, I'd be all over a 13", probably a 13" Air.
If Apple went to a 14/16" MBP design, I *might* be a little torn between the two. 14" is almost 15" and the size is really great. In the end, it would come down to specs. If I could get the same dGPU and proc/ram/ssd, the 14" might get the nod over the 16".
We'll see.... I'm eagerly awaiting. Amex in hand, cash earmarked in the savings account. Will order the day they're announced, with or without redesign. About the only thing that would keep me from ordering would be a major redesign goof, such as mimicking the 12" lack of USB 3.0, low power proc, and horrible power adapter design.