I think Newcastle and Aston Villa will also be among the teams that can get past Manchester United. It seems to me that you are very positive about Man Utd, because they have not had so many changes in the off-season to expect that they will become stronger. I know that everyone wants to believe that this is possible, but I think that they will not be able to compete for the Champions League this season, at best it will be the Eurocup zone.
The good news is that they are putting in efforts to revive the team and bring it up to standard this summer, they have made some important attacking signings and still working on signings in the midfield and a defender hopefully so it is work in progress for now. Hopefully they will be good and strong enough to compete with Newcastle, Aston Villa and the rest of the EPL teams for top four in the coming season.