I think your MCDBA is recognized forever, but as a SQL 2000 certification. SQL 2005 has the MCITPro and MCTS certifications. My guess is they will be updated for SQL Server 2008, but probably not until 2009 sometime.
If you get ss2k5 certified now, my guess is it won't be too hard to get the ss2k8 certs upgraded. It's not a big change in the product.