The PS4 isn't even announced yet and people are saying its too close to next gen :P
Since you want to play Uncharted 3, then go and get a PS3, if you can wait, some people have said it may be an idea to hold off until Gamescon is over, but I don't think its worth it. It's over 2 months away and then people will say wait until TGS, E3 is over, so now's the time to bite :)
And like many people have said, there are countless cheap games available for the PS3 now so its a great time to join the PS3 owners club :)







