In an interview with Eurogamer, Colin McComb shares his communications with Chris Avellone on a possible Torment follow-up from Torment, while also nothing Avellone is currently too tied up to be likely to work on it in any signficant fashion.
"As you may recall, Chris [Avellone] mentioned his ideas for a spiritual successor to Torment with some frequency over the summer. This stemmed (at least in part) from discussions he and I were having about the possibility of resurrecting the IP, and this led to my reaching out to Wizards of the Coast. That did not yield fruit, but it did get the two of us talking about what we'd like to see in any regard, and we both agreed that Planescape was not the best route for us to take anyway, due to the mechanical issues and editorial oversight WotC would want.
"The Project: Eternity Kickstarter took them in a different direction than a direct successor. I told Chris that I would not work on a Torment successor without his approval. We talked about it for a bit, and he told me that he was entirely comfortable with me moving forward on a Torment game without him, and he gave me his explicit blessing to do it.
"Right now he's incredibly involved with Project: Eternity, and I do not want to distract him from a project that is incredibly important to his company. With that said, I would be happy - no, wait, overjoyed - to have him on board in any capacity whatsoever."