I think it will be Russia->Sumer->Arabia->Rome->Greece->Poland
Russia now to not reveal Arabia with Saladin (anti crusader) two days after 9/11
(firaxis is very conscious and careful regarding such things)
Sumer later to "prepare" American public for Middle East
Arabia two weeks after 9/11, distanced from the mess
Rome later because they know a lot of people wait for it and hype must be built (it really works for me as I didn't care about Rome until it was being postponed again and again)
Greece almost last civ to reveal because of probabity of revealing second leader DLC as well
Poland last because I'm 95% sure it is DLC civilization
Russia now to not reveal Arabia with Saladin (anti crusader) two days after 9/11

Sumer later to "prepare" American public for Middle East
Arabia two weeks after 9/11, distanced from the mess
Rome later because they know a lot of people wait for it and hype must be built (it really works for me as I didn't care about Rome until it was being postponed again and again)
Greece almost last civ to reveal because of probabity of revealing second leader DLC as well
Poland last because I'm 95% sure it is DLC civilization