The unbranded Nexus 6 is on sale new for $499.
I'm skeptical that verizon will carry the new 2015 nexus phones that come out this year. I'm hoping they do but I think a big reason they decided to carry the nexus 6 was because of verizon's close relationship with motorola.
As long as you don't care about CDMA it shouldn't matter. If the new Nexus has the bands required to operate on Verizon it should be just a matter of transferring SIMs, like its been until recently with the Nexus 6.