The Winchesters: Supernatural Prequel Pilot Casts Sam and Dean's Parents
So this is actually happening. I remember a while ago Jensen Ackles was spearheading this and Jared Padalecki was upset that he didn't involve him. I'm guessing they made up (I'm hoping) but maybe Jensen assumed he was busy with Walker (which now has its own spinoff coming).
Looks like they're changing the timeline a bit, as in when John becomes a hunter.
Gotta say, I'm interested. Doesn't feel right not having Supernatural around, so I guess this will have to fill that void.