I thought Mueller was using the "United and Chelsea are interested in signing me" headlines as a way of getting a big wage increase at Bayern after the World Cup? I'm not sure he was that serious about leaving, and since Bayern did resign him for a much higher salary then the only way you would probably get him to United is for Bayern to decide they didn't want him, so he becomes a free agent. I can't see that happening though considering his WC success.
But the Wayne Rooney saga also happened that year, and from memory it was supposed to be the heart-to-heart talks with Ferguson that kept him at United. So, without Ferguson there's a good chance Rooney leaves, and as much as I despise the half potato man-child without Rooney they are a much weaker team. So perhaps no title for United in 20120/11?
As much a United fan as I am I seriously think we can't dominate forever - it's no fun, like, at all. I'm not against Chelsea winning 2010/11 ITTL.
For the Rooney thing, how about this (probably ASB, but let's have a go at it): after FIFA 2010 (ITTL a German win

) he decided "fuck this shit I'm leaving", so Man United traded him for Mueller, with an undisclosed amount of fee attached. Berbatov inherited No. 10, Javier Hernandez got 9, and Mueller got 14.
I'll admit the above is authorial fiat.
Marc A
P.S. Anyone else got ideas as to how would the Red Devils do w/o Fergie? I'm thinking whoever's in charge would try to get rid of old blood like Giggs and Scholes (don't have anything against them, but let's face it - they're old and not the awesome players they once were)