I actually think the opposite and they'll be doubly motivated to not miss out again. I don't think they've enough to win it but I certainly see them as a serious top 4 prospect.
Tottenham look most at risk to me to drop iout the top 4 with the combination of Wembley and no signings/ their squad already weaker. Chelsea should be pulled right back into the pack. They're massively light and an abnormal winning run/ being so injury free isn't likely to happen again. And Utd have improved with Mata giving Mourinho his leader on the field but the rest of the squad and his tendency to revert to type doesn't scare you any more than anyone else. Had you got Morata and not Lukaku I'd be far more concerned. .
There's only City if I'm looking at the other 5 that have significantly improved themselves to think they're the team you need to finish above to have any chance IMHO.