Cannot say I am sad to see them go - although I never flew ATA (but had plenty of opportunities), many friends/colleagues had very negative things to say about the carrier.
I hope that we can begin replacing some of the departing LCCs with other carriers - Virgin America will fill this gap with what I hope will be excellent service. That is, if they get off the ground!
I would selfishly love to see more int'l flights out of SFO too - we have great coverage to Asia, decent to Europe. I heard from a friend in the industry that Emirates is starting SFO-DXB nonstops on their new Airbus A340-500 although not sure if its daily; and also heard we may get one/more carriers to Europe. We added Icelandair last year, but they suspended service until May - it is seasonal (May-October). Maybe we will see Alitalia return its daily SFO-MXP, or Swiss its daily SFO-ZRH flight. Then there is Air New Zealand and Qantas; all we are really missing is Air India or maybe TG and that would be one hopping int'l terminal!
As it is now we have a lot of lift to London - 2x UA, 2x BA and 1x VS. Let's add something else for a change!