>>1
If your company uses Microsoft Servers: 2000 and/or 2003 Go with . NET. It will be much easier to implement a running server on .NET if it has .NET than to install J2EE capable servers. Besides, the mean guys at IT will bring you flowers if you went with a .NET solution.
If this is just for learning and extending your knowledge I would agree with #3. Just pick one and decide to learn, the skills are transferable.
5, 6>> You guys do not sound like professionals. How are they going to phase out .NET when it is integrated into Server 2003, 2005 server components. What is there replacement; I'll wait for this answer. I have an entire lifetime ahead of me.
#6. .NET represents the architecture the language is executing or what the component is apart of: Hence, ASP.NET, C#.NET (C# is different), VB.NET, etc...