“vNext” is the codename Microsoft has chosen for the next version of the Visual Studio.
A big feature is improving the application lifecycle management (ALM) process. Check out this pdf “Visual Studio VNext: Application Lifecyle Managment” or the video The Future of Microsoft Visual Studio Application Lifecycle Management or the blog Agile Project Management in Visual Studio ALM V.Next.
To view the IDE improvements, visit Microsoft Visual Studio IDE Futures from TechEd 2011. Lot’s of cool new features, especially when it comes to searching.
Note that the same project can be used in both VS 2010 and VS vNext. There is no upgrade wizard as a project saved in vNext can be used in VS 2010 and visa-versa.