There is a big difference between being hot and overheating. The device will easily work at 50 degrees Celsius also take into consideration that it has twice as many processors as the iPhone 5 and all of them have a much much higher clock rate (Ghz) the heat you felt was merely the extera performance.
Wait so you are ok with the phone getting too hot simply because it more processors? I don't know but when the iphone 6 gets released next year it should have quad core and I doubt it will get this hot. I also held a LG phone with a quad core in it and it ran normal. I'm hoping that was an isolated issue with that floor model and I'll find out when my unit arrives...