I've heard the plan is that it's releasing sometime this year but the current version is not able to be upgraded and should not be installed on a live server.
But you should check the demo out and see if you like it. I'm sure it won't be too much longer before it releases.
You can buy XenForo and get access to 1.x builds. You would get access to XF2 Beta builds as soon as they are released as long as your subscription is active (one year from purchase date).
If you buy XenForo now, you are effectively buying version 2, because the stable version of XenForo 2 will be released before your year of updates has passed, and therefore as soon as it is released, you will be able to download it for free. Until then, you can already download the XenForo 2 code as it currently stands, but it is a developer preview version and you should not use it on a live, public site.
I have a quick question. Will the beta be able to be used on live sites? Or should we wait until an official version. Just wondering since the topic was brought up.