I'm not sure anyone's going to be able to specifically answer your questions; mainly because those certifications are not out yet, so no one can say for sure.

Here's my background with certifications:
I'm Microsoft, Cisco and CompTIA certified.  From Microsoft, I have MCT, MCP, MCP+I, MCSE, MCSE+I and MCDBA certifications.  I've taken 36 Microsoft exams (I used to be an instructor, so taking exams was just part of the job).  The disclaimer for my response to you is that I've never taken a development exam (other than the SQL one for MCDBA).

Here's what I've learned:
Your certs don't become obsolete when a new version is released.  I'm an independent consultant and I still run into Windows 2000 stuff all the time.  Even NT 4.0 and Windows 9x from time-to-time.  It takes a long time for businesses to implement versions as they come out.

More detail, if you're interested:
My certificates go back to Windows NT 4.0 (that's where the "+I" certs come in), Windows 95, SQL 7.0, Exchange 5.0, IIS 2.0, Proxy 1.0, etc.  What I've learned through all of this is that the difference between the exams is largely dependent upon the difference between the versions.

For example, when I took the Windows 98 exam, it was extremely similar to the Windows 95 exam.  And the Windows 2000 Professional exam was very similar to the Windows NT 4.0 Workstation exam.  This is because Windows 98, in its core, was very similar to Windows 95 and Windows 2000 Pro, in its core, was very similar to Windows NT 4.0 Workstation.

However, going from SQL 7.0 to SQL 2000 was a very, very big jump.  SQL 2000 is so very different from SQL 7.0, it's almost as if they are totally different products; not just an upgrade.  The same can be said for going from NT 4.0 to Windows 2000 on the server side of things.  Windows 2000 Server (and all of the stuff in it like Active Directory and all of the network services) was such a major departure from the past it was as if one had never seen a Windows server before.

That may all seem totally irrelevant since you're looking at .NET exams, however I think that the principle applies.  In other words, if you were looking at taking a .NET 1.x based exam (like Visual Studio .NET 2003) instead of waiting for the new exams, then you'd really want to wait because .NET 1.x and VS 2003 are so primitive compared to .NET 2.0 and 3.x and VS 2005 and 2008.

I don't think, however, VS 2008 is such a huge departure from VS 2005 - and the same is true for .NET 3.x versus .NET 2.0.  So, my opinion would be go with the current exams.  Get your certification now while you're motivated and have a roadmap planned out.  Then, in the future, you can take whatever upgrade paths Microsoft offers in order to keep your certifications current.

I've trained hundreds and hundreds of people and watched them attempt to get their certifications.  My experience has been that if you start procrastinating, for whatever reason, you simply won't achieve the certification.  So, do it now and then upgrade later.

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