From the things that Tim Sweeney said, its not like a complete new engine. Its UE5 + SceneGraph/Verse(For multi thread stuff) + Publish into epic ecosystem.
The last part is the most interesting one. If Epic wants to compete with Steam they have to bring up a fully new(!!!) concept that doesn't require indie devs to spend 90% of their time on marketing.
Fortnite has a massive audience, Epic collected lots of data. Maybe they use AI to show specific games to specific people. Who knows. I really wish the age of influencers ends sooner than later.