The problem is that it's an unknown couple of months waiting for a device who's software we already know.
You can always "wait and see" on devices and you'll perpetually be waiting. Since the question was asked of someone who's on a 3GS and they want a new phone, "Wait 5 more months" isn't really a satisfying answer, in most cases.
Going from a 3.5" screen to a 4.3" screen has actually been somewhat the bane of my existence. Whereas my old phone (original Motorola Droid) was a breeze to use single-handedly, my new phone (HTC Rezound) is miserable. I am constantly having to reposition the phone in my hand to reach the far corners of the screen. Using the phone with two hands mitigates the problem, but only because I can then hold the phone with one hand as the other stretches.
Being able to view more is nice, but I am not yet convinced that it makes up for the significant decrease in usability. YMMV of course, but either way I think the increase in screen size is an interesting trend for an OS [0] spearheaded by someone affectionate toward one-handed use [1].
[0] Not that Google controls device dimensions for most devices, though I imagine they have some say in the Nexus phones.
You can always "wait and see" on devices and you'll perpetually be waiting. Since the question was asked of someone who's on a 3GS and they want a new phone, "Wait 5 more months" isn't really a satisfying answer, in most cases.