It's unlikely they'll pull EVDO devices any time soon. Verizon's been experimenting with software/hardware that will let them run their current CDMA network and LTE over the same spectrum and dynamically shift spectrum to the protocol that's seeing higher traffic according to some analysts I respect. As the existing CDMA traffic falls off, more spectrum will go to the LTE network. But they aren't about to pull the plug on millions of customers and force them to upgrade, nor are they likely to give folks a reason to switch and not pay their termination fees (dropping EVDO would probably constitute a change in contract terms).

VZW will have EVDO until they've a clear road map to LTE, and even then for a while until they can afford to dump it.