Children of Men. It's been on HDDVD forever, but it's taking it's time to Blu-Ray!
I don't really want any older movies to transfer over to Blu-Ray unless they really up the video quality and add some BD Live features. It seems kind of worthless to fork over more money for an older movie on Blu-Ray to look slightly better than it's DVD counterpart.
EDIT: Hmm, nevermind. I see Children of Men was released on December 2nd, 2008 on Amazon. It's a bit too pricey at $31.99 and it's also out of stock. This may be an import actually...
Maybe a Guy Ritchie collection on Blu-Ray (Snatch, Lock Stock, etc.) when Rock n Rolla comes out.