I would just point out that while "Planescape" is dead "Torment" isn't. WotC still maintains a trademark registration against it (Reg# 2778296, if anyone's really interested and knows TESS) so there's no inherent block to a Torment 2.
Most interesting thing about Planescape as an IP is that apparently in 2003 they were planning on making a TV series (!) in the setting as there's an expired registration against Planescape for use in TV.