Wilson's 19 years old, a Championship loan would be good for him, as I can't see a Premier League side making him their first choice striker. If he stays he'd have Rooney and probably a new, quality striker ahead of him in the pecking order. If the two strikers ahead of him stay clear of injuries, Wilson would find himself in a position where he'd only have a chance of playing in the Capital One Cup and the possibly the beginning stages of the FA Cup. An early exit from the COC like last year would take away his few chances to impress and he'd have to play in the reserves for another season.
He should follow the example of Bamford and Jordan Ibe. While Bamford is unlikely to get a chance at Chelsea due to Mourinho's alergy to young players, he's impressed in his loans. Ibe did the same thing - impressed at Derby and got a serious chance in Liverpool's first team.