Bad news for folks with unlimited data plans on Verizon looking to buy Apple’s new [purported] LTE-flavored iPhone later this year. It appears that the carrier won’t be honoring grandfathered unlimited plans in the switch to LTE.

Fierce Wireless is reporting that customers on the Big Red network will be forced to choose from a data-share plan when moving from a 3G handset to an LTE one. The news comes straight from Verizon’s CFO Fran Shammo…

“As these 3G unlimited data plan customers migrate to 4G LTE, they will have to purchase the company’s data-sare plan (which Verizon plans to launch in mid-summer) and move off the $30 per month unlimited data plan. “Everyone will be on data share,” Shammo said.”

Up until now, the carrier has been allowing customers to keep their grandfathered unlimited data plans when switching from a 3G device to one with LTE. Verizon must be seeing the same negative affects on its network from unlimited data users as AT&T’s Randall Stephenson mentioned earlier this month.

It’ll certainly be interesting to see how this plays out. Because as it sits, Sprint will be the only iPhone partner in the US offering unlimited data come this fall — LTE or not. This may wind up giving the carrier a much-needed advantage in fighting with the other, much larger carriers, for new iPhone customers.

What do you think?