Did Paris Hilton have anything to do with this? Creator Eric Kripke hinted that the fifth season might just be the last of Supernatural.

Talking to Entertainment Weekly, Kripke said,

I did set out [to] tell a five-season storyline... Quite frankly, I never expected [the show] to make it to five years. But now that we're in our fifth year, I have every intention of ending the story with a bang and not drawing it out or watering it down... That having been said, I'm looking at this season as the last chapter in this particular story. That doesn't mean there can't be a new story. Buffy did it. The X-Files did it. You close a chapter on a big mythology storyline and then you begin a new one.

This guy sounds as annoying as that damn Lost guy. If he's not keeping us suspense he's canning the show. And with this, will Jason Teague return to Smallville? Maybe with some superpowers now?

'Supernatural' to 'end with a bang' in 2010 (but there's a catch) [Entertainment Weekly]