Reports claim that Verizon and Sprint are thinking about EVDO RevB and the VZW may only rollout LTE in select areas.
One thing for sure is that CDMA can't go away until 4G coverage and reliability is as good as 2G/3G today. That will take many many years. During the transition, they may as well add RevB.
EVDO RevB was considered dead a few years ago. Is a little surprising to see it possibly revived, but it would make sense to go ahead and go for it if it's not a high cost rollout.