They haven't even figured out how to make 5 run well yet. What could go wrong with UE6? Here we are, on the eve of the launch of the new version, and the ONLY UE5 game I can think of that I can say really runs great is ARC Raiders. Am I missing one?
Unreal Engine has always beens resource hungry with inconsistent performance (except for devs that modify UE heavily). I really don't see how people are expecting UE6 to be any different. All the best uses of it will probably be the devs that modify the fuck out of it. Even something as simple as HDR has been so inconsistent on UE4 and UE5.
Eh, Fortnite is a massive platform of a game and will take some time to convert plus already got done UE5 upgrades, whereas Rocket League is so old it still has UE3 roots and even in a 60 second commercial can show some improvements.
But also I think UE5 and UE6 may stand as separate tech branches for a little bit rather than it being a straight "upgrade" that every developer falls all over themselves trying to adopt immediately, and that would make Rocket League a fair candidate to pilot it. The main thrust of making another new engine has been said to be the tacking multi threading finally, and doing that as its own instance while UE5 keeps on all the additions/fixes it has in the works would allow each to progress as needed. (And as this thread reaction points out, UE5 needs a lot still.) So a smaller but still massively adopted (in the scrutinized tournament play market, no less) game like RL would be a sensible proof case. Then UE6 could fold in UE5 features until it is caught up. UE5 as the mature old Unreal for massive projects in progress for the past few years, UE6 as the robust but evolving engine for this and future platforms.