The Nexus 6 was leaked out last night - which I still think was a fake - so we're getting closer to launch now. The Nexus 6 wasn't typically carried by carriers. Although we have seen Verizon and Sprint carry it in the past. However, that is because of the nature of their networks. It's either they carry it, or it won't work on their network, unfortunately. But T-Mobile has been carrying the Nexus ever since the beginning. T-Mobile has openly supported unlocked devices like the Nexus 4, Nexus 5, and others from outside the US. However, it is a bit more expensive at T-Mobile. Since they aren't getting it subsidized like Google is.
So what carriers will carry the Nexus 6 this year? Well if everything went well last year, I'd say T-Mobile and Sprint. I highly doubt we'll see Verizon with another Nexus before CDMA is completely gone. Once they go full on LTE and VoLTE (which is a GSM technology) we'll likely see a Nexus work on Verizon's network, as you'd be able to take an unlocked phone over there. Which is actually a pretty big deal. Will AT&T carry it? Probably not. Why? Because AT&T likes to lock down their phones and put bloat on them. Sprint and T-Mobile usually don't. If you've ever picked up a T-Mobile or Sprint phone, you'll notice there's almost no bloatware, when compared to AT&T and Verizon.
What carrier are you hoping picks up the Nexus 6 this year?