They are discussing this topic on A.net as well.
The article says "possible" buyers could be Delta, not that there is any proof Delta has shown interest in buying Virgin America. I also think DL would have a tough time getting the government to ok this type of deal.
AS, NK or B6 would have a better chance, but AS probably doesn't want s bunch of Airbus. In another article I read Virgin was looking at more of selling off a majority chunk of ownership, not necessarily a buyout from another airline.
In addition to DAL, DL would gain some valuable slots at DCA which would help since DL lost so many in the US LGA slot swap.