heres my logic, but you have to stay by it for it to work. sell your iphone 4 to your friend for 200 hold on to that money and don't touch it, put it into a savings account to earn interest. Get the 16gb iPhone 4s for free. In a year when the iphone 5 comes out sell your iphone 4s for 250 which you should realistically get for it if you keep it in good condition. Now if you didnt touch the 200 your friend gave you a year from now. youll have 450 from selling both phones (not including interest made) to spend on the iphone 5 when it comes out, and the way the new generation iphones are usually priced it should cost you 629.00 for the 16gb iphone 5 to buy it without a upgrade or new contract. Now that leaves you to spend only 179 euros for the iphone 5 without contract or upgrade, which in america is pretty much the same price if you were to get a new contract or upgrade because they dont give away free newest model iphones like your carrier. so you can go with that plan which is relatively simple.
Another plan if my currency rate calculations are correct is that you guys are paying 156 extra euros to buy the 16gb iphone 4s outright with no contract or upgrade then in america which only cost 473 euros with no contract instead of 629 euros.
Now if this is the same for the iphone 5 then you have a nice arbitrage oppurtunity since most likely the iphone 5 will be a world phone and can use it on any carrier worldwide correct me if im wrong. you could buy a brand new iphone 5 from america, for about 473 euros for a 16gb model and all you'd have to spend was a mere 23 extra euros on top of the money you made from selling your iphone 4 and 4s to get the new iphone 5 without a new contract if you followed my plan correctly.
let me know if this is to hard to understand, ill try to make it simpler if i can