Significant re-coding will be required to get ABPro to run under Joomla 4.
This work is progressing well.
A closed beta should be available when Joomla 4 goes into beta test.
I cannot guarantee that all current ABPro functionality will work in Joomla 4.
See an early ABPro 4.0.5 running under Joomla 4.0 Alpha 12 here