Mark, rather than looking at it as "UBB.threads v7.5.9", The versioning should instead be seen as "UBB.threads7 v5.9"
That is how we refer to the revisions on the development side of things. We will not be increasing the version to 7.6 until we've had the opportunity to clean a significant amount of coding over the entire package and introduce a fair amount of new features, which is where our roadmap is currently taking us.
If you take a look at the changelog you will see substantially more was done than just a little bug fixing and code cleanup, some of which you may notice performance wise as various variables have been increased with more modern servers in mind.
And we have an announcements forum at UBBDev where we've been publicly discussing several code check-ins, so one can read about upcoming changes.