reasons there won't be a larger screen:
-The 1st screen increase was in response to boom in iPhone's software abilities. There has not been another leap like that.
-Apple doesn't have to do it; they already make most of the handset profit. The market may like bigger handsets, but not Apple's market
-A new screen resolution will be a PITA and all the Apps, just updated for iOS 7, will have to be uprezzed again. Of course, if a developer programmed right, thats easy
-A bigger phone is not Apple-like IMO; its difficult to carry around. Apple devices have been becoming smaller, not larger. So a new iPhone with a bigger screen would need to be the same size or smaller. This is unlikely with todays tech. Maybe a bigger screen in iOS 9 or 10....
-Larger screen will lower battery life
-I doubt they will offer two sizes, or discontinue the 5c so quickly. That is too rapid a product line change.
What I think is more likely:
5c price drop, no touch ID
5s becomes second tier
6 with iPad mini style body, thinner maybe, sapphire maybe.
if the 5c had a touch ID I would be tempted...the metal 5s get chipped so easily.
Personally I want better battery life, comfortable to hold redesign, sapphire display, and a touch ID SDK release.