Windows 7 has the greatest chance of staying usable as it's the most popular of the out of support operating systems.
ive looked at alot of monitors over here in my life, and most people over here either use windows 10, or windows xp. i havent seen that many people using 7 (besides me and family), but the fact people still use it really shows how good that OS is. also i MAY have seen someone using something even older than xp, but i think that was just a classic skin? idunno, ill probably never find out...