Actually, here is a direct quote from the cited article. "The game has shipped more than 3 million units since its launch in early February. Shares of Take-Two were up nearly 5% in after-hours trading following the report."
And in regards to the five million estimate, that was for lifetime sales. Considering Bioshock's first month sales were a little over one million and it has gone on to sell four million, five million lifetime isn't out of the question.
And still, the five million figure was just an off the cuff estimate from a single interview. Their official projection to investors was 3 million.
http://www.edge-online.com/news/key-...es-projections