WelshBloke
Lifer
Apple has always made battery life a big priority. iPhone 4 & 4S run underclocked to save battery, iPad 3 came with a bigger battery so it can have the same battery life as iPad 2, etc. I'd be pretty surprised if iPhone 5 didn't have similar battery life to 4S.
If it has a bigger screen, a more powerful chip and LTE then the only way to do that is to make the battery physically bigger.