Yeah, as it's been said I don't envision him going above and beyond 10HR tops this year, and that's being pretty generous.
Then again, if you want a warm body at SS that has a pretty good chance at hitting .280-.300 without any sort of major HR threat, Starlin Castro may very well be your guy. Maybe in a few years he develops that power, but for this year, shoot, .300/10/75/20 would be some sort of a wet-dream of a season from the guy. I think the 20 steals are more likely (he was 10SB 8CS last year), maybe even the RBIs if he hits .300, but to give you an idea.... he was called up on May 7th and hit a HR in his first big-league at-bat (if i'm not mistaken), then he hit another HR on May 22nd. He'd hit another HR on July 24th and that'd be it for the season. He was still hitting .300ish and getting his doubles, but like, homeruns aren't his concern so I think you'd be likely to have a power hole @ SS, and I don't think he's going to give you as many SBs as the somehow-beloved Elvis Andrus for the trouble.
But hey, if your team's a juggernaught and/or you really believe in the kid, you could do worse.