Wont be surprised if the changes on Bonvoy drives members elsewhere.
For example, the loss of multiple night credits and stay based qualifications.
People who regularly book multiple rooms will definitely looking for other programs that credit those extra rooms.
Likewise, people who did plenty of short stays will looking for loyalty scheme that count stays like old SPG
Personally I book multiple rooms on some of my stays, so 2019 night count will definitely lower than 2018.
And if I cant reach any meaningful tier on Bonvoy, then I will end up moving my stays altogether to other chain.