Microsoft won't acquire npm for sure.
I highly doubt MS will ever squeeze GitHub for cash also. It's about integration and azure.
They have proved by now that they are not Oracle and they are doing the opposite of them.
- making development more open ( .net core vs Java)
- making tools more open ( eg. Sms vs MySQL, vscode, ...)
Both have clouds. Microsoft is adding/creating more free tools/services as their onboarding funnel. Development ease is their motivation.
Oracle buys popular things and starts licensing them. They try to force existing clients into their cloud ( MS makes it optional). Oracle's motivation is management influencing