Comment 8 for bug 1795892

That is correct, 5.0.0 is the most recent stable.

5.0.1 will be the next stable, to be released soon.

5.1.0 is probably 6 months out, give or take. The nightly builds are the current state of the 5.1.0 branch (although it's confusingly labelled as 6.0.0). You can run a nightly build to see what it looks like (or to help out finding bugs), but keep in mind that it is definitely not as stable as a stable release.