Now I'm hearing that the factory bluetooth is going to be a simple module that piggybacks onto the existing OnStar. That would mean that you may be able to get a dealer to retrofit it onto a 2008 Malibu after the 2009s are released.
I have also heard production on 2009s should start in mid-June, (they would take orders starting in April) so you should see the first 2009 Malibus on dealer lots any time after June depending on where they're being shipped.