Nothing. The Raspberry Pi Foundation is rather outspoken on abandoning the firmware and replacing it with regular in-kernel Linux drivers on newer hardware and has made progress on that front. Furthermore, the userpace of the firmware is all secret Broadcom code, Microsoft has only open-sourced the kernel of the Pi firmware. Older models will probably need the firmware forever.
I wonder what the implication would be for the pis?
Nothing. The Raspberry Pi Foundation is rather outspoken on abandoning the firmware and replacing it with regular in-kernel Linux drivers on newer hardware and has made progress on that front. Furthermore, the userpace of the firmware is all secret Broadcom code, Microsoft has only open-sourced the kernel of the Pi firmware. Older models will probably need the firmware forever.