So, what is really the problem? If you don't want to go further than 10, then DON'T. No one is forcing you to go past 10th prestige.
On the other hand if you reach 10 by next month, what incentive would you get if you wanna keep playing? NOTHING, but with 5 new prestiges, you can at least continue to prestige if you want to.
There are those who are in the fast lane, and 10th prestige is easy to come by.
Why is it a big deal if they add 5 or 10 more. I dont get this argument. It doesnt hurt you and it doesnt help you.
I wish I had enough time that this would be an issue... but really, what is the problem here? I like to prestige since I enjoy unlocking things and ranking up... this lets you do that longer. And as far as being unfair to people who have reset their stats? Now they can continue playing longer, seeing as they will get all the way back to 10 before the next iteration of the game at their current rate of playing anyway...