We already know the 32GB Nexus 7 exists. Some guy actually got one by mistake - in Japan. We've seen it at online stores in the US, online stores in Europe, and even Canada. It is bar-none Google's worst-kept secret ever.
What we have not seen, though, is a 32GB Nexus 7 actually physically in these United States. As of today, we know they're here - at Staples.
So yes, the Nexus 7 32GB is 100% imminent. We're fully expecting it to be announced at Google's October 29th event in New York, along with the Nexus 4, and Android 4.2.