He probably will grow into a LB or DE, but there is a trend towards taller Safeties that is starting in the NFL. A guy like Kam Chancellor in Seattle is one of the best Safeties in the league and every bit of 6'3 230. I just read an article about how other teams are looking at that Seattle secondary and wanting to add some big, tall guys to their defensive backfields as well.
You see Hubbard listed at 6'5 or 6'6. But if those numbers are inflated a bit, like they are for almost every high school prospect, and he is closer to 6'3 or 6'4, there is a chance he maybe sticks at Safety or Star.
The game is constantly evolving and one of the big things in recent years is these huge former basketball player type TEs like Jimmy Graham, Kyle Rudolph, etc. As players at all positions seem to get bigger and faster, the next development could be tall, athletic 230 pound safeties who can combat these tall pass catching TEs and the Calvin Johnson, AJ Green, Julio Jones type WRs.
Edit to add: It will be interesting to see if he attends any combines and we get an official height. Mike Brewster for example was the same as Hubbard in that he was always listed at 6'6 or occasionally 6'5. At the NFL combine, he was 6'2 and change.
http://www.nfl.com/combine/profiles/michael-brewster?id=2532803
If Hubbard is legitimately 6'5+ you almost have to project him as a LEO. If his height is inflated a couple inches like most HS kids, I think you probably project him as a LB, Star or Safety. I almost hope he is a bit shorter as we have really targeted a lot of these long, athletic DB/LB tweeners like Darron Lee and Chris Worley and if one of these guys develops into a player with the size and physicality of a LB and coverage ability of a DB, it would be a huge boost to our defense going forward and a real strategic advantage.