I don't know much about NFL, mostly rugby having played it my whole life. But I reckon Wade can make it. He may need a bit of time though. Rugby players can bring something different to football, skills current players don't have or don't utilise. In the small amount of football I've watched, I've noticed few running backs use a fend or an effective fend (handoff), they take the tackle. In rugby you don't want to get tackled, because if you don't have support you will lose possession. This means players are more motivated to evade would be tacklers. And I've noticed football players don't step (I think you guys call it cut) in the same way rugby players do i.e a good player like Wade will step and not lose pace or slow down, break his stride, whereas I've seen football players kind of stutter as they change direction, slowing down, allowing the defence to catch them. Also the tackling seems pretty poor, technique is all over the place, something Wade could take advantage of. Playing international rugby, you miss tackles, you're out of a job.
As far as adapting to the game, I've read that pundits have said that he's missing 15+ years of experience. Which isn't quite true. There are a lot of cross over skills, some very similar running lines and also moves e.g the snap. As a wing, Wade would have run a very similar move as blindside wing. And rugby is a very complex game, with a lot of players needing a varied skillset. Wade would be expected to kick, catch high balls, tackle and run all sorts of different running lines. So coming into football, being given different lines to run or different skills to adopt is not going to be a foreign concept for him. Rugby players are used to having to adapt to new skills. As a wing, he would naturally look for open space, whereas football he runs for the blockers. Kind of counter-intuitive, for him, but also rugby players at times deliberately aim for a tackler, rather than space. So they are very adaptable and pretty smart. You have to be switched on to play rugby at the highest level.