And of course once nobody's using Windows, attackers will pivot to target whatever everyone's switched to in its place. And they'll find holes. They always do.
Check out the DEFCON 2018 talk "Through the Eyes of the Attacker" to see to what lengths the TRITON attackers went. These guys were dumping eeproms from boards running obscure MIPS processors and were looking at raw ethernet packets in Wireshark and flipping bits in the packets to see what would happen. That their command&control was running on Windows was just coincidence.
Very few adversaries have enough resources to break anything. The threshold for roughing up a Windows setup is the lowest in the industry.