Microsoft already has VSTS which has source hosting, CI, issue tracking, kanban, release management and more.

I suspect acquiring GitHub was more about the developer mind-share than the technology.

Are you sure that VSTS will live more than two more years? I'd suspect that Microsoft will eventually want to integrate GitHub with their CI and get rid of TFS (of which VSTS is just a hosted version) entirely. I don't know if you've used TFS/VSTS but it's not exactly user-friendly and well designed. Especially their CI configuration is horrendous.

Nat answered this in the AMA: They intend to develop both, and ensure VSTS users can use GitHub easily for version control if they want to.

But bear in mind, extremely long-term support for business workflows is Microsoft's obsession: Even if they decided to "retire" VSTS, it'd probably get updates for the next decade or so.

VSTS hosts git repos as well. I don't know of anyone that still uses TFS, but I'm sure they exist. I've been using VSTS daily for the last year and a half, and while it has it's quirks I think it's a powerful and productive environment.

Team Foundation Server is more than Team Foundation Version Control.

An online toolchain would be a nice concept in theory, but at least on my laptop, performance is still an issue.

Online IDEs still eat up a lot more resources.

WASM might help make them a lot more performant, and I think online editors could be a place where it really shines.

Microsoft does have Monaco used in Azure and VSTS online tooling.