Jay P. Kapur of the Media Center TV Team confirmed at AVS Forum that Vista will not need an NTSC Tuner!  This means you can use ATSC Tuners and/or CableCARD’s without needing a separate NTSC Tuner installed.  Vista Beta 2 still needs the NTSC Tuner, but the final will not.  Previously, Media Center has keyed the ATSC EPG Data off of the selected NTSC Lineup.

News Source: AVS Forum/ Vista Discussion