The sack numbers just aren't there...I know he was a NT and all, but there will also be a number of DTs getting in from "his" era, probably moreso than other eras and I think it leaves him out.
Aaron Donald, Kevin Williams, Ndamukong Suh, Geno Atkins are, IMO the guys that should be in. Ridiculous sack numbers from the position. I, personally, think Gerald McCoy should get in...
But then you get to contemporaries like Haloti Ngata, Fletcher Cox that should be in line before him.
Its just a long road for Vince, IMO. Only 16 career sacks is going to be tough in an era where you've got guys going in with over 60.
Maybe much much later, but he's got a long wait if so, IMO.