Well ... Microsoft certainly know about Frontier Developments, and there has been a big name backer we haven't been told about (which let's be honest, we don't need to know and it is none of our business). I'd say that IF Frontier get big enough, there is certainly a good chance Microsoft would buy them out ... and I wouldn't blame David Braben if he did sell to Microsoft.
Your post incites me to wish that Frontier brings clarifications