That delay on The Binding of Isaac: Repentance is a short one, as the final expansion for one of the most beloved roguelikes of all time is coming on March 31st, 2021. That'll be almost three years after it was announced, but it was only supposed to release in December. December to March is a hell of a lot less time than a lot of other games were delayed by 2020's nonsense.
Developer Edmund McMillen has posted a trailer for Repentance to Steam, a nice little summary of how I feel about the game, which is crying on the floor. Anyways, the Repentance expansion is a cool concept, based around the hugely popular Antibirth mod for the game and made in collaboration with that mod's authors. It's such a huge expansion that it's basically a sequel to the original. Some 130 items, a hundred new enemies, 25 bosses, and thousands of new rooms join the game.
In the post accompanying the new trailer, McMillen said that they were waiting until March for polish reasons. "We just want all of its features to be perfect and testing to be a bit more in-depth than our last little release that will go unnamed," he said. That's polite. I'll go ahead and name the last release as The Legend of Bum-bo, which was unfortunately just a good and fun game rather than a genre-upending instant classic. McMillen and other developers will post more update blogs to the Steam page as release approaches.
The Binding of Isaac first released back in 2011 as part of the very first wave of the roguelike revival, and has gotten more than a few expansions and/or updates since, including full-game overhaul Rebirth in 2014. You can find it on Steam and on Humble.