[citation needed]
Visual Studio Online (which is pretty much TFS in the cloud) is alive and well. And improvements made to VSO have been shipping regularly as updates to accompanying TFS on-prem.
Are you confusing TFS with Team Foundation Version Control (TFVC)? TFVC is also pretty popular as a Visual SourceSafe replacement and has been very stable for us, though the recent support of Git in Visual Studio and TFS has us considering it as an alternate workflow for some smaller projects. I think the support of Git is great, but knowing MS (and what they've said through their usual surrogates) I don't think TFVC is going anywhere anytime soon.