I just realized that since 4.25 got released very recently, the 4.26 release target will probably be sometime in fall. If UE5 beta is supposed to start during Q1 2021, and the release cycle is roughly 4-5 months, then 4.27 would end up Q1 2021 as well. So that got me thinking 4.26 may indeed be the last UE4 release, as it would not make much sense to develop UE4 and UE5 at the same time after that, and rather focus all development resources (aside from 4.26 maintenance and bug fixing) on UE5. So I am starting a bit of a UE5 hype thread here 
Yeah! Hypeeee!! But to be honest, with 4.26 preview 7 released this week, I think there will be 4.27 before UE5. What are you guys most hyped about? I am working with chaos system for 8 months already, and I have to admit, it’s pretty good as a real-time engine, but it’s rather crappy designed. Really. I cannot event get position of individual custers in any way. And that’s such a critical functionality! They need to work on it a lot. Anyway, my team is currently working on an awesome shooter with chaos & niagara. Can’t wait for UE5 though. That will be such an exciting year for game development!
Source build of branch ‘master’ says 4.27. I think we’re still some ways from UE5, since I believe it was said we could expect it in late 2021.
But I don’t think we’ll have to wait too long anymore to try some of the new UE5 features in UE4. I love how fast and smooth ray tracing already is on my hardware!
EDIT: I’m guessing the thing that would really indicate that we’re on UE5 would be a UI-overhaul. UE4 and UE5 don’t appear to fundamentally be very different. At least, not to the extend UE3 and 4 were. I think a lot of the new features will go in testing phase before this UI overhaul.