Well I don't know much about it either but I suspect since they had to pretty much upgrade everything to get 3G here I'm sure that 4G will be an easy upgrade. I think getting the bandwidth here was the major thing, so they probably had to run fiber since edge didn't need much bandwidth. If that's the case then future upgrades (LTE) will be easy now. It might already be 4G (HSPA+) who knows. I don't have a 4G phone. And I can't see Thumb Cellular providing the speeds Verizon will be, even if they are considered "4G" lol. Plus I'm sure they will be putting caps on soon since Verizon just started... and their data plans will probably be more money/lower caps than Verizon. And let's face it, it would cost them way too much money to give everyone more than 5Mbps around here. That's why you don't see many local wireless internet companies around here offering too fast of speeds. It costs little companies too much money. In your face Thumb Cellular! Lol
That map on the AT&T site is changed every month. Over the past several months they have added AND removed many areas of the country from the 3G coverage "coming soon" areas, and have even completely stopped labeling anything as "coming soon". A large part of Oklahoma was labeled as coming soon in March and has since been dropped completely. Typical AT&T, tease and then never deliver.
They have also seemingly taken down the 4G coverage map, referring to HSPA+. There was a subset of maps detailing HSPA+ coverage which showed areas like Lansing, MI partially covered, but that is gone now.