Despite working on multiple expansions for the simplistic dungeon crawler The Binding of Isaac, the developer behind the game, Edmund McMillen, has indeed been working on a new project that he says he's looking forward to revealing soon.
The announcement came in at the bottom of a post that McMillen made on The Binding of Isaac's site where he was detailing the contents of the most recent mod pack to be included in the game. There, at the end of the post, he casually introduced the teaser about his new project that he's working on with programmer Tyler Glaiel.
"On a side note not many of you know this but Tyler and i have been in crunch mode for the past 3 months trying to finish this secret project," he wrote in his post. "We are coming close to announcing it and its release date, so keep and eye out for it, i dont want to spoil the fun yet but i can say this. Its hard, its weird, its personal, its has amazing controls, its a totally new unannounced IP and its easily one of the largest games ive ever made level wise."
While there's not a lot to go off of based on his most recent announcements, there are a few things that can be ruled out. The "totally new unannounced IP" part of his post tells us that the new project is not The Legend of Bum-bo or Øuroboros, two games which have already been previously announced by McMillen.. There's not too much that's been revealed about many of his projects, though, as McMillen has a history of making his announcements vague and cryptic. The Legend of Bum-bo is described as a "turn based puzzle RPG type thingy" by McMillen, so even if there is soon news announced about the secretive project that he and Glaiel are working on, there's no telling how much can be learned from it.
McMillen's Afterbirth+, an expansion of The Binding of Isaac, recently made it's way over to the Nintendo Switch. McMillen has commented that The Binding of Isaac will benefit from continued work and community-inspired mod packs in the future in addition to his work on other projects.