NaviServer 5 is more of an evolution than a revolution, therefore it will be fully compatible with the NaviServer 4.99 series. As Linus framed it many years ago, we are "running out of fingers and toes" for counting the version numbers.
The tip version on Bitbucket is what we have so far
- ns_set reform (better scalability, optionally also available for 4.99)
- ns_http with persistent connections
- Tcl9 compatibility (Tcl9 is in some respects still a moving target, we will probably wait with the official 5.0 release until Tcl9 is released)
- Improved crypto support (e.g. Argon2)
- Upgrade of Licensing (from Mozilla Public License 1.1 to Mozilla Public License 2.0, eases packaging for large distros)
... plus various other changes.