Going on loan isn't about seeing if he's good enough to play for us though. A loan is just for young players to get a regular chance to practice and learn and in the case of the big clubs, for them to get those chances away from the glare of the first team and the big stage. It's also about teaching some discipline I guess, that's why Fergie used to say anyway. Loans from big clubs are about lots of things...but it's very rarely a case of, well go and prove yourself at another team and if you do well then we might consider you.
Playing at United will be totally different, at United he will be moving about playing in different roles, against different tactics, alongside another quality of players. He could go to Hull or something and score 15 goals and it would mean nothing for us as a barometer to judge him on.
We can disagree about how good/bad we think he is, that's just a matter of our opinions. But I don't see the advantage in binning him now, why? We don't gain anything from that. He's not leading the line for us, we're not reliant on him for goals...he's not clogging up the wage bill or taking minutes away from other players who need them. So why not just let him have a year more, 2 years more...and if at 25 yeah he's nowhere near making it and holding others back then let him go. On the other hand there's plenty to be gained if he does well.
It's just pure frustration to say get rid of him now. Makes no sense.