Heh. That was a middle-of-the-night panic talking :-) There will be no 6.3.1 release. I'll release 6.4 when appropriate.
Plans
I'll fix the crasher affecting leoflexx.py in devel.
I'll merge the ekr-undo branch into devel only after Leonistas have tested the ekr-undo branch for several weeks.
For leoInteg, imo the most important thing is for Félix to release the leoInteg plugin officially. That can be done at any time based on Leo 6.3. Once that crucial milestone has been passed, it should be relatively straightforward for Félix to track changes when Leo 6.4 goes out the door.
Summary
There will be no 6.3.1 release. For the foreseeable future, it will suffice to make improvements in the devel branch.
Leo 6.4 is scheduled for after the sabbatical. 6.4 may go out the door earlier depending on how pleased I am with the undo work.
Edward