We should loan him to a bundesliga team or sell him with a buyback clause.
I think thats the best way to find out if the player is good enough, Real Madrid does it often with fairly good results.
If we keep him his chances of playing are really slim, he is 5th choice at best after Maguire, Lindelof, Smalling and Jones. He will hardly get minutes.
If we loan him to another EPL club he wont be a starter, the most likely scenario is that he will become just a squad player at best. No team risks having a youngster as a starter in order to develop him just to send him back to his original club, they would get all the mistakes and wont enjoy the final article. So we just end up just wasting a season, we have seen this time and time again.
Meanwhile in the bundesliga they seem to risk a lot more with youngsters, by selling him we warrant that the club that buys him will give him minutes if they think he’s good enough. If he shows talent we can buy him back and the other club makes a profit, and if he doesn't make it then we got rid of deadwood. It's a win-win situation.
I think we should do this for every youngster that can’t make an instant impact on the team. That way we don't end up having players like Wilson on loan after loan just waiting for his contract to expire. We may end up getting some interesting developed players or at least make a little profit out of them.