I can't see Microsoft do that. Not because of any disliking of the linux community, but because it poses a real threat to them.
This would basically allow (for instance) Google to reverse engeneer Windows and put all the bits it likes into a free Chrome OS. Not bad for end users, but terrible for Microsoft itsself.
Also Microsoft currently rules the business end of computing. Giving up their patent rights would make it more viable for others to enter the market with similar code.
Not that this would not be good for everyone. More choice, cheaper software etc. Microsoft remains a business run by financial motives. There seems to be no reason that alligns with their financial motives to remove their patents (development they spent billions on).