As we've mentioned on the project calls and elsewhere, the current plan is to release v3.10 of GNU Radio prior to GRCon (Sept 20-24, go register here: events.gnuradio.org/e/grcon21
). 3.10 is a much smaller step from 3.9 than was 3.8 from 3.7 or 3.9 from 3.8. There are, however, some things that could impact your OOTs in the process of migration - but we haven't captured all of them yet, only that there is some more c++ modernization (up to c++17 features) and changes to includes in headers.
We encourage OOT authors to follow the branching strategy of the main gnuradio repo, that is the master branch in the OOT should be compatible with the master branch in gnuradio, maint-3.9 compatible with maint-3.9, etc.
So as you migrate your OOTs to work with the master branch, please note any special steps involved by editing the wiki here:
as it will be useful to the entire community. Or, just respond to this email if you don't want to bother with the wiki.
Again, I'm hoping the step is very small, but would be great to figure out earlier rather than later, and any issues in the main codebase can be ironed out and/or documented ahead of the release.