According to that page, if:

I am currently working toward my MCTS or MCPD on Visual Studio 2005
Then

Continue your learning track on Visual Studio 2005 so that you are ready to transition to Visual Studio 2008 when the time is right.
I think this is a corporate way of saying "Well, we don't want you to feel bad, so we'll work something out for you."

To be honest, I'd say go for the latest - 3.5 - wait for it. I don't know why that page has a <title> of "Get certified on Windows Server 2008" though.