The iphone 5s is just going to be a turbo'd 5. I dont forsee them changing the body, screen, button placement...well anything to the body at ALL. Same phone externally, maybe a new camera... definitely a new processor and gpu. Thats about it.
If they change out the body for something else(larger?). The EXTREME amount of accessories(that everyone LOVES) for the iphone will sharply decline. Same reason you dont see much in regards to accessories for the android phones. They burned alot of accessory makers when they changed to lightning(they didnt need to). So changing the phone again after one year(out of the norm) would REALLY hurt the accessory makers that plan on selling the cases (battery cases, waterproof cases), and what ever else that is iphone 5 specific for the 5s as well. Also most of the apps are finally updated to the screen size of the 5. Developers wouldnt be all that happy.
Basically, them changing the form of the new iphone that has yet to be released, would hurt us as consumers. Heck we dont even have apple certified battery cases shipping yet!
Ok....well, i think i got off subject,
If you dont want LTE or the larger screen wait for the 5s. Simple as that
If you do, go get your self one.
I havent had any problems with my 5 so far.