Well, we may never sign/trade for one. But one thing that has been proven pretty certain in the NBA is that major star players get traded, normally once every year or two. Look at it this way, in the past like 5-7 years we've seen Kevin Love, Carmelo Anthony, James Harden, Dwight Howard, Deron Williams (when he was still a star) Ray Allen, Kevin Garnett and lesser names like Ty Lawson, Rajon Rondo, Enes Kanter, Eric Bledsoe and the like, be traded.
Star players get traded with a fair amount of frequency in the NBA. The key is to put yourself in the best possible position to make a trade when one becomes available to you, which I think we've done better than almost anyone in the league.
I think a lot of what happens from here on depends on Our young guys and the Brooklyn picks. If we get two top 12 picks (a distinct possibility, with a solid chance of one Top-6/7 pick) next summer, I think we'll make a serious move some time shortly afterwards.