Despite having released a whole bunch of games through its sixteen years of existence, Mediatonic wasn't a relatively household name until Fall Guys: Ultimate Knockout's success. It would seem that some of the higher-ups at Epic Games just realised how talented the developer studio is as well.
Epic Games confirms it has bought Tonic Games Group (Mediatonic's parent company). Both parties are apparently well-aware of the fact that some gamers become worried when hearing this, so they've released an FAQ answering some of the obvious questions. This makes it clear that Fall Guys: Ultimate Knockout won't change in terms of its gameplay, as all platforms will continue to be supported with new content, seasons and updates. It also states that Fall Guys will remain purchasable on Steam, but we'll see how long that lasts considering Epic said something similar a year before it removed Rocket League from Valve's service after purchasing Psyonix.