Major props to the Mavs. They are slaying their demon.
The way I see it, the same rules apply as applied in the Suns/Lakers series: Mavericks have 2 chances to close it out in games 5 and 6. I said if the Suns series went 7 the Suns would win, and I think the same holds true here. If the Spurs win 2 straight and take it back to San Antonio, I think they win the series.
With that said, I don't see this series going 7. Spurs might make things interesting with a win in game 5, but this series won't make it past 6.