I have not yet had a chance to look to see if the config.inc.php is the same or not. I would guess it's not the same, thus the scripts would need to be changed around to support the new version. You're more than welcome to poke at it until we do. If the old configs for 2.x.x. works with 3.x.x then you can install it, if not, then the new config.inc.php has to be changed for our setup.
Everything I have seen indicates that phpmyadmin is independent of DirectAdmin. I don't see where they cross paths other than the link in DirectAdmin which takes you out of DirectAdmin and into phpmyadmin.
I wouldn't imagine it will be too long until we support it. No eta's, but I wouldn't imagine more than a week.
Correct, that phpMyAdmin is essentially independant of DA. It just needs apache, php and mysql.
The setup for phpMyAdmin that needs to be done is to set it to use a login/pass method. There is a method where the login/pass is stored in the config.inc.php, and other settings like that to get it to work with mysql the way we have it set.