I'd be very surprised if he should succeed at United. He has not steadied the ship with us (Bayern), and our situation was relatively calm in comparison to United's prolonged state of disarray.
His stint with us has pretty much destroyed his image of a brilliant tactician and football mastermind for me. We had very little variety in tactical setups, and our attack was mostly stunted, while our defensive record did not make up for it.
Additionally he was undermining of players publicly in press conferences repeatedly, and also complaining about the overall squad.
With a hodgepodge squad of low on confidence players like United's, this is a recipe for disaster of Jose-esque proportions (3rd season, before anyone asks).