Larian may be using a new game engine, but they would have had to have started with it some time ago.
Projects D and E are scheduled for release next year (hopefully before the world ends, but a slip into early 2013 wouldn't be inconceivable).
Status update (long overdue)Both were in a presentable state for the Game Developers Conference in March (
Status update), and the earliest I recall Larian confirming they had started working on Divinity 3 was October of last year (see
here, with the first details
here).
