GitHub do for developers what Microsoft want to do for the rest of business through SharePoint.
Maybe they could add Office 365 editing to GitHub and pitch it as the successor to SharePoint. Or try to integrate it with their other products in some kind of Frankenstein mess.
They seem to be doing much better with these things lately though. MS Teams is incredibly good. VSTS is pretty nice as well. I'm frankly unsure why they'd take on Github, other than better integration points into Azure services, CI/CD and other tooling for commercial/enterprise users.
Maybe they could add Office 365 editing to GitHub and pitch it as the successor to SharePoint. Or try to integrate it with their other products in some kind of Frankenstein mess.