Actually their current plan is to introduce all-LTE phones sometime next year. Obviously, they'll need a strong, nationwide voLTE deployment for it, but they plan to shift away from CDMA in a big way. They'll keep the network around for a while (a few years) to fill coverage gaps/for the stragglers, but all-LTE phones won't be using the CDMA networks.
Of course this does not necessarily mean that the network is going to be opened up a la GSM--in fact, if we go by the precedent the Uncarrier has set, access to voLTE can be restricted.
Right. The current network certification requirements for phones, as I understand them, require IMEI whitelisting. The presence of Verizon-friendly CDMA may be one requirement behind a phone getting approved. CDMA bands aren't hard to put in phones, and I'm guessing neither is flashing. The hard part therefore has to be getting the CDMA carriers to approve the phone.