http://gs.statcounter.com/ios-version-market-share/mobile-ta... shows 12.3 at around 50%, so the question for me would be what percentage of that long tail would upgrade within any reasonable extension period. Public news might actually accelerate that since it gives people a reason not to procrastinate hitting that button.

I’m not sure of the stats honestly but there’s still going to be a huge long tail of people on earlier versions for months afterwards. I was surprised that I was still on iOS 12.2.