According to a news article posted in the Press section here, they have already offloaded most of their coins. I was very disappointed when I heard the news. They bought their coins in 2012, when the exchange rate was like $5 per coin. They should have shown a bit more patience. But I can't blame them either. A lot of people are giving up... And I am about to offload some 45% of my coins very soon.
Hmm, I don't see that about the Winklevii selling any coin anywhere especially the Press section:
https://bitcointalk.org/index.php?board=77.0
I did a quick Google News search as well and came up empty. I think you misread an article or are mistaken.