Nexus 5 prepaid options

So, I'm looking to buy a nexus 5 (or whatever its going to be called) when it is released. I am currently on a At&t plan with the rest of my family. I'm hoping that it will be available on contract for at&t (what do you guys think the chances are?) But if not what do you think are the best prepaid services? I live in Metro Detroit so i have pretty solid coverage on at&t. i definitely want LTE coverage. Thanks in advance guys.