I can't speak specifically on MM.NET, but in general, yes. VS2010 (don't bother with 2008 at this point) supports multi-targetting. So, you can edit with VS2010 and target the .NET 2 runtime that shipped with VS2005.
But I think what you're really asking is... Can you load the .NET 2 - targeted code and recompile in .NET 4? In general, yes. The .sln will be converted, but everything else *should* work.
>Is there going to be any problems moving my application from MM 2.3 and VS 2005 to MM 3.6 and VS 2008 (2010)?
>
>Can I just copy the code to the new version?
>
>Are there any code changes that have to be made?
>
>Thanks.
Craig Berntson
MCSD, Microsoft .Net MVP, Grape City Community Influencer