Showtime should not have any direct influence on the DVDs. MGM might refrain any releases until syndication of the series begins. That probably will not occur for a few years (longer if Showtime keeps sitting on the new episodes). Also MGM doesn't appear (at least to my eyes) a consistent policy towards TV on DVD stuff. When it all comes down to it, your guess is as good as ours.
As for Season 2, the last word that JMS heard was for a September start. All 15 episodes should be in the can already.