It's not actually a direct sequel to Torment, but rather a spiritual and thematic successor in a new setting. How so? They can't use the Planescape setting itself.
Still, you have the original creators of the Planescape setting, a writer and concept artist from Torment, Chris Avellone's blessing and, of course, Brian Fargo who headed up Interplay at the time. It's an exciting project and fascinating prospect for fans of the original game.
A couple more links:
http://www.rockpapershotgun.com/2013...orment-sequel/
And a link to the website of the actual new setting:
http://www.numenera.com/