Yes, in the case of BuddyPress, they are going to benefit in increasing the requirements.
I would jump straight to WP 5.9 as a minimum, inspired by WooCommerce, which has a similar immense task of migrating widgets and shortcodes to blocks.

I wish for Buddy press to reboot successfully. The way how scripts and stylesheets are being loaded currently mixed with blocks is an unnecessary edm mix to their own ears. ;)
Maintaining compatibility to the last 2 WP releases instead of 4 versions, could ease the process.