Video Gamer has a lengthy interview with Telltale CEO Dan Connors. It's mostly about Tales of Monkey Island (with some minor plot spoilers on the direction Episode 2 is heading). Also, this:
VideoGamer.com: After Tales of Monkey Island, what's next for Telltale? Is there a known IP you're currently looking at, or might we see something completely original from you guys?Here's the full interview.
DC: We're looking at a bunch of different IP, and we've got a few original designs floating around the studio we're getting closer and closer to a position to green-light.
Update: More "Dan Connors in long article goodness" here at Now Gamer.
Source: Video Gamer
And if all is well, and everyone is happy with the returns and the model, I would imagine they'd be concentrating on at least one more MI season before thinking about other LucasArts properties.