I recently just got on board with sprint for the iPhone 4S in December, however presuming the iPhone "5" will come out in roughly October, I would want to upgrade to it. Now I was wondering if we signed a 3rd user to our family plan and he(father) got the iPhone 5, if I could give him my 4s and transfer my number to his iPhone 5 and use that as my device. Is this possible?
You can. It's a super-easy process. You'll order the iPhone5 on the new line, activate it on your #, and re-activate the 4S on your father's number. I was able to take care of it onine when my daughter was eligible for upgrade and my wife wanted the 4S.