I don't even think they go above 4.0", which would be the killer for me. Yes, 4" (or even 3.5") is adequate, but I'm decent height with decent sized hands and a 4.6" phone seems about right for me. Heck, even the Galaxy Note seemed OK sized to me, though I think I would prefer 4.6"
Now if...
While I'd love an iPhone with a 4.3" or greater screen I'm expecting another 3.5" actually. (Maybe 4" in almost same size phone) Not sure what the 4.6" screen rumors were about, but I actually think that 4.6" would be too big for many iPhoners.
Another 3.5 or 4.0" screen iPhone will keep...