TFS has first-class support for Git repositories (in addition to the classic TFSVC repositories). So yes, they're moving more and more to Git. But no, they're not abandoning TFS.

Interestingly, however, most of their "open source" efforts (.NET, C#, and related) are all on GitHub rather than their own hosted offerings: CodePlex (which is basically dead) or "Visual Studio Team Services".

I'm a Microsoft employee on the Git team.

Microsoft is moving to Git and we use Team Services / TFS as our Git server for all private repositories. GitHub is only used for OSS since that's where the OSS community is.

Reading release notes of TFS, they seem to be putting much more effort into improving integration with Git compared with TFVC. This may be just to catch up to acheive parity with TFVC in TFS, but it was enough for me to abandon TFVC for Git in all new projects.

Team Foundation Server supports both git and TFSVC.

You can use TFS with Git. Git will act as the underlying SCM.