They need to make the big signings now if they want to stay top.. only Ferguson knows how to manage this team and lets face it it has many Mediocre players Or too young to be considered top class yet.
Rooney, Van Persie are the only ones i would consider world class.
Vidic would definitely be up there but he's had a bad season that was plagued with injury and you can only see him going downwards from here. Ferdinand is no longer what he used to be and the same goes for evra. In Midfield Carrick was phenomenal this season but this was arguably his best season by far and he's aged 31 so you can't rely on him to produce the same next season especially without Sir Alex's managment.
The bright things about this is that Phil Jones is destined for a great career, Rafael has improved dramatically and De Gea is nothing like he was at the start of the season. I think Phil Jones is ready to step in for Ferdinand. and if the rumours are true David moyes is going there he might be able to convince Leighton baines to come with him. That would make for an upgrade in the defensive line which was arguably their worst department this season. Early season they've been conceding goals left and right.
In Midfield I think they need a make over because like i said I don't think carrick will produce the same stellar season he produced this year.. But I personally think David Moyes will back him up and stick with him but if not getting Ilkay Gundogan from Dortmund isn't a bad idea but otherwise sticking to Carrick is also ok. However I think the manchester united midfield lacks Steel. and as i said before if david moyes is comming he can also bring in Fellaini. Also In My opinion they need one HUGE signing to give them the edge on the wing. Valencia is not bad, but they'd need a LM that can make the difference and i think Manchester United can easily fund a move(By Selling the fringe players) for Ronaldo or Bale to join them with Bale being the more realistic target.
In my opinion up front doesn't need any work, after all they've got the sensational Van Persie and reliable Rooney. However if Rooney leaves i think Kagawa is perfectly fine as a replacement and they can use the Rooney money and Fringe players money to Spend on: Gundogan, Baines, Fellaini, Bale/Ronaldo (3/4 is fine but Bale or Ronaldo imo are a must).
Their team should look like this:
De Gea
Rafael Jones Vidic Baines
Fellaini Carrick
Valencia Rooney Bale
Van Persie
sorry if this post was too long.. I really just get way too into it when the topic is about football :P Im just so passionate about it that i've never posted something this long :/ and im surprised only after typing how much i wrote.