Unlocked At&t LTE device?

Hey Guys what's up. I'm currently thinking about Leaving VZW because I really can't afford them right now lol. Love the service but I feel like I'm being ripped off. I'm thinking about switching back to Sprint since they have LTE up and running now (not in my cities yet Boston and NY) But it'll be here sooner than later. 

But I want to make sure I'm on a network that will allow me to have an Unlocked Nexus Device when they start rolling out at the end of the year.

I know it's possible to have an Unlocked HSPA+ Device, but will it be possible to have an Unlocked At&t Verison from Google WITH LTE? Or will the Unlocked devices be stuck with HSPA+?

Thanks.