Do I need to bring in my iPhone 4S to upgrade to an iPhone 5?

Do I need to bring in my iPhone 4S to upgrade to an iPhone 5?

In a couple of months time will you want to then upgrade to the iPhone 5s? Why do you want to upgrade to a 5 when a 4S is nearly just as good? We're talking very slightly faster, very slightly larger screen, you won't notice that much difference.