Dirt Rally 2 is 4 years old.
And that's about it. Do you know how well Unreal handles complex calculations required for the type of game KSP is? Of course you don't. Meanwhile completely omitting the mountain of work required to switch engines, get a new team experienced in such engine... Pretty much rewriting the game from scratch. Do you really want KSP2 EA 0.1.0 in 2035?
Yes, and it would introduce physics bugs Unreal has.
Stop the fantasies, it ain't gonna happen, not this far into the development.