Someone on the Football Ramble made a really good point I think in regards to Ten Haag, who most United fans now seem to want and expect in the Summer.
Basically saying that, despite his current success, he's a long way from being a sure thing when he moves on and that managing Ajax is probably the easiest job in football. This being because they base everything on bringing young players through - young players that have grown up playing the exact same system that the first team plays and are ready to slot in as soon they are good enough. That's clearly completely different to the model that United operate with, so he will need to adapt and adapt fast.