They are due for a resurgance and that will be the expectation when Yao comes back, even before he plays a game. Phoenix will probably not win 50 this year and that is what it will take to make the postseason (again), so there's room for Houston.
However, remember your recent history. The Houston Rockets did this "best team in the lottery" in 2002-03. The follow-up season they didn't improve much, even with Yao having a terrific season in 2003-04, and the celebrated hiring of Jeff Van Gundy. They were everyone's favorite to make it big. The same thing happened after they traded for Tracy McGrady, the next Shaq and Kobe tandem. The Rockets have a recent history of not meeting expectations. Miami these past two seasons has defied them. You can blame the poor Eastern Conference, but things haven't worked out in Yao's time there.
My point? Put bluntly, shut up. Wait (and demand) that they do something before you put them in the upper echelon of NBA teams.