I share diophan's concerns - if the vintage playerbase is too small, league matches will never fire (and the vintage playerbase is VERY small on MTGO). If you recall, a while back dailies went from "never firing" to "almost always firing" when they cut the number of Daily time slots. Switching to leagues is basically raising the number of Daily time slots to infinite.
I'm trying to remain cautiously optimistic, though. If we hit critical mass of players, the league experience is much better for streaming than the daily experience, and it's possible the playerbase has grown since before ... it's also possible that the league format attracts new players, particularly players from outside the US who don't have a daily scheduled at a convenient time for them right now.