Here we are in 2021 and already the delay announcements are hitting. Fortunately for fans, this delay announcement is a bit on the shorter side. Developer Edmund McMillen says that despite the desire to get The Binding of Isaac: Repentance out in December 2020, he needs some extra time for polish. As such, the game won't see a release until March 31, 2021.
The expansion has been in development for roughly three years now. Maybe a three month delay...