I understand your reasoning why we should keep Dan, but you have stated that his minutes will be limited, and also the likes of Elanga and Amad, plus Hannibal and Shoretire, will be desperate to get a start in some matches this season, and who knows what the ceiling of these players are unless we give them games. It wouldn't surprise me if Elanga went on loan this coming season, but the other three I feel will stay.
I like Dan James, his work rate is second to none, but as other posters have mentioned, his stock at Old Trafford is possibly the highest it is going to get, so personally I would cash in now.