We can forget about Liverpool and City. Unless they have a meltdown of literally historical proportions, they'll finish above United next season. Chelsea are signing some of the highest rated European youngsters to bolster an attack that was already looking quite dangerous towards the end of last season. Shaky defence won't matter much if they can just score a bucketload of goals, which doesn't seem that outlandish. And even with their current squad, United finished above them only on the virtue of goal difference. If they strengthen and United don't, that doesn't exactly bode well for us, does it?
Spurs and Arsenal are the big doubts, naturally. Spurs have a good squad but they are managed by Mourinho. Arsenal are Arsenal. But they're not the only worries. Leicester and Wolves could easily push United for the last UCL place, as could some unknown black horse that has a great season next year.
United not strengthening and trying to coast next season is criminally negligent. We already saw that the squad is painfully thin, and the first 11 (the only players in the squad Ole trusts) can't play all game every game. And that is before we factor in injuries: if Pogba or Bruno goes down, United are screwed. They will be targeted hard, because by next season everyone knows they are the crucial players that drive the entire team, so it's not beyond the realm of possibility. United will also be playing in the Champions League, so Ole can't just send out the kids to play some tractor drivers from Eastern Bolovia and give the first team a rest.
Next season will be very hard indeed.