That would be a mistake, in my opinion. He'd at least be a top 10 pick, and likely still a top 5 pick if he comes out this year, and would get to rehab with an NBA training staff. If he went back to UK and struggled, his stock could plummet.
Bill Simmons wrote about this not too long ago. Apparently every player gets randomly tested 4 times during the NBA season, and they can take place anytime from October to June. But if your 4th test ends up being like late after game 68 or something that season you aren't being tested again until the next season starts, so you can pretty much but whatever the hell you want in your body for the playoff run and offseason.
These Bulls/Celtics games are always such ugly affairs.
In regards to the NBA drug tests they definitely are massive jokes, but its interesting that people have gotten busted, but none of which were stars at the time. Especially because we all know the league puts its superstars on the highest of pedestals (I'd say more than any other league)