A huge chunk of long time users of any software are reluctant to change
A huge chunk of long time users would switch in a blink (pun intended).
The condition is that the new version is better and no so much inferior to the old version.
New Opera probably set the world record in lowest adoption rate in 12 months.
Most long time users did installed Opera 15-23 but never actually stopped using Opera 12 as their main browser.