EDIT: On a more serious note, I do agree that Bethesda is currently enjoying the protection of making great games, but the alienation of their fanbase is slowly eroding that (I know several PC players that are getting PO'd at bethesda for their treatment to PS3 gamers.)
Me included.
If they came out and said it's not coming I think it would relieve alot of anxiety in people. But many who are still hopeful would uproar, saying after all the time you've taken to try and get it running, and all the silence, and blah blah blah, that they're just gonna come right out and say, "nope

"
After learning about their track record I'd find it much more efficient to stop freaking selling to the PS3. They can't make a non broken game then stop making the games. Other companies do it and I have no problem with it.
But all they want is money, and they know that with enough hype people will buy anything no matter how broken it is. And with promises of fixes, they'll stay behaved.
People who have dawnguard some are stuck in game breaking bugs. And again, the only reason I say that PC even got dawnguard is because of the existence of console commands.
And console commands don't help everone.
There have been cases where people couldn't help each other or figure it out on their own, so they emailed bethesda for a fix. And like a month later they get an email saying delete all saves, uninstall both dawnguard AND skyrim, and then reinstall and start over.
Typically it worked for people, but can you imagine how angry the people would be to give up their lvl 75 mage or whatever just to play the content that they just paid for and added on?