How many people will drive away from photoshop paid monthly, specially if you don’t work professionally daily on the photoshop?
Hard to tell.
I assume Adobe marketing did research on this before Adobe’s unfortunate decision and in the absence of a strong competitor they feel confident that most users will stick with Photoshop (and other CS programs).
…in the absence of a strong competitor…
But Adobe does have a powerful competitor: themselves. Many of us find it very attractive to stick with CS6 or earlier—just long enough to provide a smart blow to Adobe's bottom line, say four or five years.