Waiting for what? Are you sure you will be still alive till summer?
If you want it get it....You may resell it later for a newer one...
I just picked up an 3GS now wihout simlock and im happy with it.
You may get sick everey minute and then die soon and then you wasted alot of your lifetime with waiting for what? The newer iphone wont be as cheap as thatone now or?
Honestly look at your priorities. If you end up losing money due to missing a call on your phone, then waiting was a mistake. If you're just wanting to play sudoku, then you can wait it out.
Also, you can resell the phone and use that money for a later upgrade.
Don't get me wrong, it's a good deal. But assuming you can wait, then you should wait, in my opinion of course. If for some reason you can't then gogogo for it.