StarWars.com confirmed the Sith will be the next line months ago. When Obi-Wan went up for pre-order they said a Sith will be coming in the next few announcements. Well, its been a few announcements and we know they will be announcing a new line with the next figure. Sith is 99.9% confirmed.
I still think RotS Mace fight Palpatine will be first. Or Dooku. Palpatine would have Mace, Anakin, and Kit to go with and Dooku had Anakin and Obi-Wan (and Mace if you want it from AotC). Maul would only have Qui-gon to go with. I'm not saying it won't be Maul. I'd be pleased if it was Maul, but considering the 1/4's preventing certain versions of characters being made, I'd think the 1/1 busts would have a similar effect.
I think Qui-gon can be posed with anyone he wants to. He can be a spirit or just non-movie accurate. The pose of all 6 Jedi on the "mouth off and Win" page seems like a good set up to me. Its not movie accurate, but it looks cool.