You might want to investigate a little before you post. Gonzalez ran a 4.49 at the combine. Jimmy Graham ran a 4.56. Gates a 4.60. Those numbers are as fast or faster than a lot of WRs in the NFL.
It's probably a moot point anyway, since it's unlikely to happen, but if Wagner went that route, he almost certainly would be considered a TE prospect. At 6'5" - 6'7" and around 235 lbs, there is almost no way the NFL would view him as a WR.
Personally, I wish he would try. If he was willing to put in the work, I think he'd have a good shot to make a roster, perhaps initially as a practice squad developmental guy, but the potential definitely is there.