I like 4" but I liked 3.5" and couldn't go back to that. If it's thinner and not too bulky then I'd be okay with a larger phone. I used a 4.7" phone before and the only bonus was it was nicer for web browsing but I was conscious of it being too large.
No one here truly knows. The rumor mill would lead us to believe the next iPhone will be larger then 4".
Keep in mind the iPhone in its current form has a lot of bezel space. Putting a larger screen on the current or near current form factor is not out of the realm of possibility.
Apple has invested a lot of talk into one hand usage and overall ease of use to throw that all by the wayside. That is the reason I'm looking forward to the next iPhone.