They have two fundamental tasks related to performance. One is to deal with true 64 bit operation. The other is to deal with multi-tasking on a basic level as opposed to high level like they did on drawings.
64 bit presents all kinds of problems because all of a sudden pointers get bigger. This effects all kinds of things in a program like the handles for objects and a lot of data structures. If you look in SW help you can't but notice that there is a long string of licences that SW uses. All those vendors are going to have to get on board first before SW can really go 64 bit IMHO.
Multi tasking/multicore support probably will have to follow down the same lines.
My best guess is that SW will take a wait and see on 64 bit. If 64/32 stops the griping about lack of memory for large assemblies and doesn't have too many bugs then those that really want to put everything in the assembly will still be left out in the cold. The big question is how fast will people implement the 64/32 version? If it is too slow SW may just say people aren't going for it.
I was looking at TigerDirect last night and 64 bit mobo/cpu bundles are really getting down to affordable prices in the $400 range. People who build their own systems could probably justify a mobo upgrade at these prices. However, MSoft is apparenlty only going to distribute XP64 through OEMs. Even so, OEM versions of MSoft OS have not been hard to get.