I think Bron has a shot at 10 boards simply because I think they will be pusing the tempo alot more, resulting in more opportunities. Plus, they don't really have any dominant rebounders. Bosh is good, but definitely not a dominant guy on the glass. I think Bron is the best rebounder on the team, and if he really wanted to, could easily average 12+ a game because of his unmatched athletic ability. His playing style obviously hasn't allowed him to, but if he adjusts, like he is going to need to, I definitely see his rebounds increasing, potentially to double digits.
As for defense, I think with the type of athletes they have in Bron, Wade, and Bosh, they should generally stick with the gimmicky style of defense, although against other elite teams, they are going to have to knuckle up and play lockdown defense, which I think they are capable of doing.