Is he going to get playing time abroad? I know that many of the Euro leagues are notoriously slow about giving young kids minutes. That's a broad generalization, but before making a commitment like this, I'd want a firm guarantee that I was getting at least 30 minutes per game.
No, actually it's exactly the opposite, plenty of 17-18 kids have pro experience, mostly since there is no college basketball to speak of. So if you're skilled enough, you play. I don't think though that any team that's trying to win anything in Europe will give a minute guarantee to an unproven US high-school kid.
It's my understanding that these kids are signed to professional contracts, but their floor time is inconsistent.
Draftexpress seems to confirm this view, as almost all of their top young international prospects are averaging less than 20 minutes per game. Even Ricky Rubio, the phenom, averaged right around 20 minutes last season. This is a kid projected to go top-five in the draft.
Based on that, I think it's still going to make sense for most good college prospects to attend a major NCAA program, where they get top coaching, exposure, and minutes.