We'll probably do a port specifically for Team Arena depending on how it's implemented. I'm not going to hold my breath. It would take a lot to get me to leave my cushy job in television. If the right things were to fall in place though, who knows. It's a different animal really.
Single player is total story telling, like writing a book or making a movie.
Sometimes in single player I find myself rushing my map making in order to get to the end or to the next cool part. Multiplayer maps are more like a single work of art. I'm not sure which I like better. I had started a project a while back for Half-Life Opposing Forces. Maybe I'll finish it after Alliance 2.0 is released.