Do you have a timeline for the 5.10.1 release
The timeline for the release was actually the EuroTcl/OpenACS conference (this summer). As it was announced at the conference, "just" the documentation (Changelog summary of 45K lines Changelog, if i remember correctly) was missing. I'll take this as an opportunity to bring this up again internally.
Tcl9 should be released by the end of this year, and - judging from the large number of changes required in tcllib to make it Tcl9 compliant - it is not unlikely that there will be as well many changes in OpenACS. Therefore, it might be a good idea for having also OpenACS 5.10.1 out this year to provide a "stable" version and to continue with the tcl9 compliant version in a different branch.