Those who abused tethering racking up huge data use is most likely the reason why Verizon is getting rid of the unlimited data plan. They might as well continue racking up the GBs because they won't be able to soon enough.
Other than this topic is getting out of hand IMO. The point has been made numerous times. If people want to do things illegal it will continue. It's like a lock on a car. It only keeps honest people honest, those that want in that car are still going to get it in it.
Besides that, and back to the post I was quoting, the fact is that Verizon has shown it "grandfather's" plans, so it will be new customers not those currently on unlimited that get tiered. Verizon will probably give those on unlimited 3G now some sort of incentive (such as keeping there unlimited) to upgrade to 4G.
It's been shown by track record that verizon does things like this.