Twice now I've seen this feature mentioned as being part of the expansion, yet never with any specific details to it. It was mentioned by Dennish Shirk in context of tourism and it's non cultural victory usages in an interview, and this article also supports the idea that it will happen through tourism. I wonder how it will work, will it be like the old culture, tiles being flipped one at a time till a city finally falls, or will it be only for cities as that seems to be the only form of flipping that has been mentioned, now given that that is the more important part of the mechanic than the individual tiles so it is less likely to be mentioned. It will probably be a matter of the relative strength of the offensive civ to the culture of the defending civ, and people might already want to build up culture to keep someone from winning culturally. Also I wonder how people feel about this mechanic, if it is to be reintroduced, given that, from what I know, it was a very polarized topic in previous installations. I personally had a very love/hate relationship with this feature in civ4, loved to play builder and use culture aggresivly taking tiles and maybe even a city or two, but whenever I didn't focus on culture it was the most annoying thing ever to defend yourself against. So it is with mixed feelings that it seems this feature is returning to civ.