Check it, you can register for 70-620 now. Here's the prep guide. http://www.microsoft.com/learning/exams/70-620.mspx
This is the core Vista exam (affectionately known as 'big vista') that, when passed, earns an Microsoft Certified Technology Specialist (MCTS) certification...which is the foundation or pre-requisite for Microsoft Certified IT Professional (MCITP): Enterprise Support or MCITP: Consumer Support.
For those of you who aren't clear on why there is no MCSE or MCDST mentioned in relation to Vista.... this is because we've CHANGED the structure for certifications for all new MSFT technology releases. The MCTS level is the technology series, to validate that you know how MS technology works... the MCITP series demonstrates that you know how to TCB* using the technology. The whole idea, here, is to make the certifications more specific (so employers understand exactly what you know how to do) and make the exam paths more succinct (so less time/money for you to earn the certification you need). For more info, you can review the VIsta cert live meeting on the Vista upgrade page .
*Take care of business