Many people aren't eligble for upgrades yet for 4G phones. I'm not until July. So why would I get one know if I have to pay full price? Also many that have upgraded in the last year didn't have 4G in their area.
As others have mentioned high price is also a factor. Many people will upgrade to phones that are free or under $100. Taking away "new every 2" didn't help any.
Also many people are still on unlimited plans. "double the data" offers aren't going to convince them to give that up. Not to mention that "double the data" should actually be the norm and Verizon needs to offer double that. Also offer FREE tethering not charge $20 for it.
Also Verizon needs to offer family data plans like they have for minutes and texting. Also they need a cheaper data plans for lite users if they insist on making data plans mandatory. Until Verizon makes someof these changes I don't think they are very serious about getting people to switch to 4G or hell ANY smartphone. I know people that will stay with feature phones until Verizon no longer offers them as long as Verizon insists on $30 for a data plan they'll never use.