Ludeon Studios, developers of sci-fi colony construction sim RimWorld, have announced in a Steam update that the game will be moving over from Unity to the studio's own in-house Waylith Engine in its upcoming update 1.7. Ludeon states that the game will "look and play exactly the same", but performance will see an improvement of around 2-4x.
Update 1.7 on Waylith promises "faster startup time, game load time with big mod lists, map generation, world generation, general ticks-per-second, and just about everything else", with an example given that "a modpack with 1500 mods went from 14 minutes to 6 minutes to load." While this would be a pretty major improvement in itself, the simple fact that community mods still work after an engine switch is what really impresses and slightly confounds me here. Ludeon notes that some may appear as "potentially unsupported" due to the version changing, but will still function just the same. Saves also can be carried over from 1.6 to 1.7, meaning there'll be no loss of progress just for updating.