He means he's working on an expansion for a game other than Dominion, not that he's working on a new game that is also titled "Dominion".
Yes, it's an expansion for an unpublished game. It was an easy project and we were playing the game anyway. It's looking good but no doubt more stuff will change before it's done.
Gauntlet of Fools is unlikely to get an expansion. I guess it will have one shot at anything more happening with it, which is, BGA may put up a version of it. If they do then conceivably that will cause any interest at all in this game. Currently it is just an invisible game, no-one has heard of it and it sells very few copies. We liked it a lot, it was popular among the people at game nights who playtested it, but it did not catch on. I would point at the bidding, the fact that it's a bidding game with only one round of bidding. So some people decide, I don't know what to bid, no bidding for me this time, and then hey where were the decisions, what a stupid game.