I need to move some existing code to the TFS server on visualstudio.com. It is currently associated with a TFS server on my local dev machine. I don't care about history.
Using Visual Studio 2012 Update 3 I select File/Source Control/Advanced/Change Source Control
I then choose Unbind on each project. Selecting "Bind" then just binds it back to the original server with no option for changing it to the Azure server.
VS 2010 used to have more options for this. I work in several environments and will have to connect to several different TFS servers from time to time. I have to become free from any unreasonable ties to one particular server.