See the locked 86 page thread on the Official Forums. Their PR guy confirmed that it was in fact part of the reason with little explanation. Then a page or two later tries to retract the statement.
The damned game was nearing gold why else would they delay for six to eight months? If they need more polish do you really think it would take them that much longer?
Also if polish is indeed the main reason do you really think they would spend six more months just polishing? It's all about marketing. My guess is they could stop or just continue with the current marketing and then put out the ads for the console release. I highly doubt the sales for the PC version would falter because of it.
The game looks fantastic and the PC market is starved for this type of game. How could they lose by releasing the PC version first?
Edit: Here's the link, see page two fourth post down by the OP. No, I didn't read the entire 86 pages. After four pages I pretty much got the gist of it...http://dragonage.bioware.com/forums/viewtopic.html?topic=666477&forum=135 This comment was edited on Feb 15, 2009, 18:35.