I looked up next year's Free Agent class, and here are the unrestricted free agents. A lot of them aren't even worth discussing, I've bolded the ones who we might have even the slightest chance of signing:
LBJ - won't sign here
Durant - won't sign here
Dwight - won't sign here
Drummond
Horford - won't sign here
Pau - won't sign here / too old
Wade - won't sign here / too old
Conley - not a position of need
DeRozan - blech
Noah - blech, too broken
Parsons - blech
Duncan - hahaha
Kobe - hahaha, won't sign here, too old, too broken
Jefferson - blech
Dirk - hahaha, won't sign here, too old
Rondo - not a position of need
Whiteside
Hibbert - blech
Clarkson - not a position of need
Jennings - not a position of need
Mosgov
Nic
Deng - blech, too old
Turner
Smoove - blech
Green
Johnson - too old
West - too old
I could go on, but it's pretty clear that we're not going to sign a superstar next summer, and even a star is a long-shot. In order to get another star/superstar or two we need to draft 'em or trade for 'em. And right now the only two stars that I can see potentially being on the trading block are Melo and Cousins. I hate (HATE!) Melo, but given the weakness of the wing position he'd probably be the most bang for our buck.