I'm sure he is probably still obligated to put out music with them as he probably signed some sort of deal for solo work. Remember the press release from Wind-Up on Creed's activities, what was it back in December '03 or so?, it said the both Mark and Stapp were working on solo projects as well as the compilation CD. I'm guessing they wrapped both Mark and Stapp up with solo contracts. But I don't know that for sure.
As for how it will be marketed, I'm sure that the little sticker on the album will say former lead singer of Creed. Labels due it all the time, look at Sting or Sammy Hagar (after he left VH) or Peter Cetera or Slash. The list could go on and on. I do think Wind-Up tried to capture the Creed fans for AB right away though as the album came out, what was it?, 2 months after the breakup was official. But they also tried the same thing with the Passion songs album and mentioned Scott right on the cover as this being his first musical offering in 3 years and being the former lead singer of Creed. I don't think the artists have that much say in how it is marketed.