SP2 is available for Vista now via Windows update. Has been available for some weeks for people with Technet/MSDN subscriptions, and therefore has also been available via Torrent.
DX11 will become available when it's finished, and the DX10.1 that Vista has now will be upgradeable at that time. To be honest, this is hardly an issue now since there are no publicly available DX11 GPUs.