Supposedly, people have been successful at porting to gvoice while requesting a new number on VZW at the same time. Since gvoice takes a while to port(24 hours) but you can get a new number right away, when the port finally goes through, VZW doesn't see it as a port because the number is free and just sitting there and gives it to gvoice anyway. I wasn't willing to risk something getting fucked up and paying 2x ETFs, so I waited until end of contract.
Oh well, lose out on selling a couple grandfathered unlimited plans, but it certainly simplifies things. I was kinda weary of handing my account over to some stranger, even if I got my phone numbers off the accounts cleanly.