I wouldn't be optimistic that the store will be there for Xmas 2012. They have completely demolished the existing structure and begun constructing a new shell, which is exactly what happened with the Primark store about 500 yards up Princes St - it took at least 12 months to construct, fit out and open up and that was only a clothes shop! Given the state of the development just now and the fact that it includes a hotel as well, I can't imagine they'll be throwing the building up in 4 months.
More excuses to visit Glasgow.......
Still, at least the new authorised repair centre is only about 50 yards from my flat. It would have been nice if they had opened it when my MBP actually needed servicing though