Hi Cindy,
Unfortunately we don't yet have a firm release timeline. Artefactual has been recently blessed with the problem of having a bit too much work, which is good long-term for the projects, but also makes all of the unsponsored work around release preparation, testing, and packaging more challenging to schedule for our small company. Right now my best estimate would be the second or third quarter of 2022, but this may depend on several factors.
Most of the major feature development is done, but there are several issues around memory management we've been trying to investigate to ensure a stable release. You can see everything that is currently confirmed to be included in the 2.7 release here:
Given that 2.6 includes both a number of enhancements and bug fixes as well as two minor security patch releases, I would still recommend upgrading to 2.6.4 sooner than later if possible, even if it may mean upgrading again later this year.
Regards,