Atlassian are working incredibly hard to control the dev stack. Tight integration between Jira, Confluence, BitBucket. Bringing documentation, development, estimation, backlog together in a unified view.
Microsoft now have all the pieces. Office 365 managing users and the business side, SharePoint, GitHub, Azure, Teams.
When they start working to unify/integrate these pieces together in to a seamless experience so you can communicate, plan, build, track and deploy all on the Microsoft stack it’ll be very compelling product for businesses and very difficult for any competitor to compete. Not only would Atlassian need Jira/Confluence for example, they’d need their own Cloud for you to deploy to.