If they sold that well... there would have been more.
Warner Bros. wanted more, but they were unwilling to produce them at a higher budget. J. Michael Straczynski declared that this was a deal breaker, and walked away from making any further installments. Without his involvement, any further DVD movies became dead in the water.
Sales were actually pretty reasonable, according to all sources.
The economics of Babylon 5 are completely different than Star Trek, that 75 minute 'movie' probably cost less to make than a single 42 minute episode of Enterprise.
Oh, the 75 minute "movie" was made for dirt cheap--less than the cost of an episode of BABYLON 5, even. But CBS Paramount, if they wanted to make as much money as possible, could easily produce similarly budgeted installments of STAR TREK on DVD/Blu-Ray. It would probably suffer the same problems as "The Lost Tales," which would be a limited number of actors, extras, sets, and visual effects.
Of course, this is all speculation. Personally, I have heavy doubts that the model that the OP proposes could be sustained at all--there's just too much free programming on TV, as well as dirt cheap programming on Netflix and cable, to attract a large enough customer base to fund a new STAR TREK series. The Straight-to-DVD route might be more viable, but there hasn't been any indication that it would be sustainable.