ProjectM
Having Sonar as a desktop application that integrates with a cloud based colab and sharing service would be really awesome. No more dropboxing files all over the world when you need someone somewhere else to record on your songs. Just click a button and a version of the project is available in the cloud servers. When your colaborator is done, you update the local project and there it is. I may be dreaming of impossible things, however, I work across borders a lot and would certainly welcome something like this!
what you describe sounds like standard centralised version control, used by software devs for years... anyone who's used visual studio with tfs or git will know what i mean... and if it is implemented in a similar way to the team explorer part of vs then it could actually be a very useful thing... the one big difference i see is that it's a single cloud server owned and run by bandlab, rather than that server part also being available as a product to host on-premises oneself