I don't think that we'll sign another attacker/winger/attacking midfielder if Rooney stays. On Rooney, RVP, Mata, Januzaj and Welbeck we have quality. I suspect that one of Kagawa/Chicharito and one of Nani/Young will leave so here we have 7 players for 4 positions. I think that it mighe be enough and Powell will return to be the eighth player there.
Ideally I would like to sign two midfielders but it won't happen. Moyes likely has some plans for Fellaini and I can't see him shipping Cleverley (despite being a bad player) yet. Both of them will given a chance next season. And Carrick and Fletcher are still there. Ideally we need a very great midfielder to sign cause there is only one position left for. For that reason I didn't want to sign Cabaye this winter (though he would have been perect in the summer instead of Fellaini) and I hope that in summer we go for someone who is top quality (Vidal by far the best one).
We definitely need a left back with Evra going. My preferred choice would be Coentrao. Shaw might have higher potential but he isn't experienced and with the second choice (Buttner) being shit, I wouldn't trust to go with him as our main left back.
And finally, with Rio leaving and possibly Vidic leaving too we need a CB. That might change if Vidic stays another season. That CB ideally should be as old as Evans, not someone young. We have Smalling and Jones for that.
So I think that at most we will see 3 players coming in on the summer (CB, CM and LB, hopefully of the highest qality), Powell and possibly Zaha returning and around 5-6 players leaving the club (Vidic, Rio, Evra, Giggs, Chicharito and Nani).