Unlikely. iOS 13 (13.1) adoption is already 20% a week after release, effectively on par with iOS 12 at that time.

88% of iOS users don't even know what any of this means, and are blindly installing or auto-updating their devices.

This should in theory increase the number of iOS users because who doesn't want a jail broken iPhone. I know I am going to switch from Android once a proper method is available. They should make it work for the new iPhone only instead in the future to increase sales.

Why would I avoid an OS update over a bootrom exploit?

I'm guessing people will downgrade to more stable version of OS. Also downgrade for 32 bit apps.

I doubt enough to make an adoption rate dent. But, I do have some 32 bit apps I wouldn't mind playing around with for a bit. Some synths and a game or two.