Looks like the HTC Vive will be at Prime this year as part of their world tour..
http://blog.htc.com/2015/07/the-htc-vive-world-tour-is-here/
I hope more details show up soon as I'm super excited to try it out. I tried the Rift last year and wasn't very impressed with it. I've been reading several hands on impressions for the Vive and it sounds really really good.
Posts
(Although this does say at most stops so PAX might be different)
ref blog.htc.com/2015/07/htc-vive-world-tour-faqs/
be interested to see how big the queues are when they are in Seattle for the Dota International earlier in August