They could just as easily remain extremely bad for a long time, which is what usually happens with poorly run teams(of which I consider the Suns).
What's most likely is that, several years down the road, they'll pick up enough second-tier talent to become one of those "rising" teams that people talk about, like the current Grizzlies or the Hawks. And yet I doubt that anyone outside of their most devoted fans believes that the Grizzlies or Hawks have an elite core and are going to contend for a title in this wave. They might sneak into a conference finals or two, but, for this generation, the Grizzlies will always be behind the Thunder and the Hawks will always be behind the Bulls.
What goes down must come up. No team in the league holds steady, not for long, except in very rare cases where an elite nucleus stays together for many consecutive years (Jordan/Pippen, Malone/Stockton, Duncan/Parker/Ginobili). And so the draft ensures that, as a group, the bad teams will start to catch up to the good ones, and eventually teams move from one pool to another. What can't be predicted is how high any team's next good wave will take it. The Grizzlies are on an upswing but won't get much higher than they are now; the Hawks have plateaued and will start to come back down in a couple of years; the Blazers looked like they might have something going, but have been derailed by injuries and have to start again; the Knicks might figure out how to make a modest push in the next couple of years, but obviously you can't "rebuild" around a 28-year-old Carmelo Anthony and have any realistic dreams of a title.
The Suns will get their turn. It might be in three years, or five, or eight. But the overwhelming likelihood is that the Suns' next surge will fall short of the ultimate goal, because that is just how the league works.
Since the Suns entered the league, only
one franchise, the Lakers, has more appearances in the Western Conference Finals. No one needs to be told that other teams have won titles, while the Suns have been shut out, but that hand-wringing self-pitying distracts us from the fact that the Suns and their fan base have been extremely fortunate. From now on, they'll be just like anyone else, and it will be less satisfying, not more so.