Some people make it sound like 4.7" is a small, incremental increase compared to 4". I disagree. Every time I hold a 4.7" Android phone in my hand, I'm surprised by how much bigger it is. I will never get used to it. IF they really introduce an iPhone 6 with a minimum size of 4.7, I will probably buy a 5S an keep it running for as long as I can.
I really, really, REALLY hope that all the 5.5" rumors are bogus, and the iPhone 6 comes with a choice of 4" and 4.7", all else being equal.
EDIT: Actually, that's what I personally believe is the more likely scenario. This is exactly how bogus rumors get started: One credible source say there will be two sizes. Another credible source say there will be a 4.7" model. Some jerkoff analyst conclude that then there must be a larger one, ignoring the obvious: A 4" phone is still the single best selling phone on the market, why would Apple kill that size?
Obviously, when this gets announced, Apple is doomed for failing to match the analysts' expectations, that goes without saying...