I'd really like to see a new Discworld video game but I can't see any likely genre that it would fit into apart from the traditional adventure or role-playing game.
Sadly, I don't think that the recent, if brief, revival in adventure gaming has been anywhere near strong enough to reestablish it as a mainstream gaming genre like it was in its heyday. The time around the release of LucasArts' Grim Fandango in 1998 is widely suggested to be the signal of the end of the adventure game's popularity and a sad confirmation of its decline.
I think that with this in mind, the idea of a new Discworld game is very unlikely; unless it has the potential within itself to bring the genre back to its former glory! I just don't think that any developer or publisher would take the risk.
Although I've really missed the days of Discworld I, Discworld II and Discworld Noir, I'd rather see no game at all than a poor reincarnation of the original games. I always loved the idea of a Dicworld Online video game, but we already have the Discworld MUD.
I really do hope that my predictions are wrong, though!
Very best wishes,