If Scholes and Giggs both retire in the summer, I really can't see Fergie not going for a big midfielder, unless Cleverley and Anderson both pretty much stay in top form and uninjured.
Bearing in mind Anderson has had his obligatory good 4-5 games, broken down again, and it'll probably be late Feb before he's fit/back into form again, I can't see that happening.
We certainly can't go into next season with just Carrick, Cleverley, Anderson, Fletcher and a very green Powell.
Why would he go for a big midfielder to replace a couple of squad players? As world class players they are already gone, they have been for a long time, you don't need to replace them with other world class players when they leave. As first choice players they've already been replaced.
They've not been replaced very well admittedly, but if you bring in a world class midfielder in summer after Scholes and Giggs retire he's not replacing them because he'll have a completely different role, he'd be taking Cleverley or Anderson or Carrick's role, and one of those players would be taking over Scholes and/or Giggs'.
Even in numerical terms, Fergie will struggle to say we've got good cover without those two.
No he won't, it's easy to make a case for the midfield for next year even without Scholes and Giggs.
He'll include Jones as an option in midfield, it'll finally be Anderson's time to step up (again), Cleverley's development will be continuing, we'll still have Carrick, Rafael can play in midfield if need be, and so on, Kagawa will be included as a midfielder (might be valid if we move to the diamond), he might think Powell is an option there next season.
Central midfield isn't Ferguson's priority. He's consistently decided to focus on all the other areas of the team and ignore central midfield, regardless of retirements, regardless of having mediocre, elderly, crocked or severely ill players as major options, there's no reason to think he's going to change this summer because we might lose a couple of squad players. He's so uninterested in making acquisitions there that he thinks Giggs can play until 2015.