Ok, it seems that MySQL AB is finally committing to fix up PDO_MySQL and to generally accept the fact that PDO is the future. Of course mysqli will also be actively maintained. But they will also make mysqlnd play nicely with PDO etc.
There's budgets and time lines for the project so things are already moving along and developers to the project will soon be assigned. Lukas also mentions updated on PHP's side - validating that the documentation for the extensions (mysql and mysqli) are up to date and correct.