I've now looked at 40 years of drafts (1970 through 2009) and there were 73 players who were repeat all-stars among 200 players drafted in the top 5 (36.5%). It's important to point out that among those 73 players were quite a few two-time-and-done all-stars, especially in the 90's, who would not be considered superstars by any stretch of the definition, but they are included here nonetheless for lack of a better metric.
Now, to be clear, I am not arguing that you shouldn't draft and develop young players. Trading away high picks is dumb unless you can get an established and relatively young star or someone on the cusp of stardom in return. But, given those odds, any team that tanks on purpose to secure high draft picks will probably not be rewarded much for their efforts.
Now entertain this scenario. The Suns end up with say #4 overall and use it to draft someone. That player will likely be better than a Wes Johnson (#4 pick two years ago) but probably won't become a repeat all-star. This will undoubtedly be seen as failure to meet expectations and the Suns organization and scouting department will be heavily criticized by many, especially if a player drafted a few spots later by another team ends up becoming a superstar. But, in fact, this scenario is very much to be expected, given the history of hit and miss, mostly miss, when it comes to the NBA draft. In fact to expect that player to become a perennial all-star would be ignorant of the fact that the vast majority of players, even those drafted in top-5, never become one. And getting it right, especially in the lottery, has a lot more to do with luck than scouting ability, imo.