The teaser and the idea of a gigantic dungeon hearken back to Baldur's Gate/Icewind Dale much more than PST. Still look like something I'd want to play.
The "true" PST successor is Torment: Tides of Numenara [1]. Though it's not set in the same universe (Wotc being too busy not doing anything with the Planescape setting to license it), it will be more focused on existential questions than dragon-slaying. As a bonus, it won't feature adapted 2nd edition D&D rules.
The "true" PST successor is Torment: Tides of Numenara [1]. Though it's not set in the same universe (Wotc being too busy not doing anything with the Planescape setting to license it), it will be more focused on existential questions than dragon-slaying. As a bonus, it won't feature adapted 2nd edition D&D rules.
1: http://www.kickstarter.com/projects/inxile/torment-tides-of-...