After AT&T pulled a data plan switcheroo on their customers, a concerned Sprint customer wondered if the same thing would happen to him. So he emailed Sprint CEO Dan Hesse and asked.
https://gizmodo.com/at-t-iphone-tethering-an-extra-20-month-if-you-abando-5553135
The reply?
One can never say ‘never,’ but [Sprint] has no current plans to change our pricing.”
Good on them. [Engadget]