This rumor been hanging around since SW started the codeshare. If you look at the changes ATA has gone trhough since the agreement, it looks like it has been shaped for an easier fit.
regional feeder= sold
routes to compliment SWA with no overlap= done
737 base alignment to PHX, LAX (LAS), SFO = in progress
trading in 757-300's for more 737's (-300's&700's)= in progress
737-800 Etops=in progress, done by September.
A decreasing ATA presence in IND. (hangars and admin. buildings)
Also:
Ever increasing codeshare city pairs.
SWA linking ATA cities for sale on thier website.
SW computer booking ability to create international passenger name records.
Is SWA taking over the remainder of ATA? A lot of ancedotal evidence, you make the call. I'm not counting on it, but I'm not counting it out.