Dave, the colors on the SB edition are horrible and this isn't a film that would benefit from 5.1 remixes. Sony will revisit this one at some point, but quite frankly, the current edition is excellent. But if MGM could bag the Criterion commentary to Raging Bull then maybe Sony could acquire the commentary to Taxi Driver from Criterion.
Donnie, what would be the point of a slipcase reissue? You'd buy that, would you? Who cares about the packaging.