So as far as a third rdr game i think its inevitable given the success of Redemption. However I was shocked to see someone wanted it to be post WWI. Now they are entitled to their opinion and as such a must respect that, just as I hope they will respect mine in that this would ruin the franchise. Don't get me wrong I think this is a very interesting time in history and I am very much looking forward to LA Noir. That said one of the best things about the RDR series is it is set in the Old West.
This is an entirely untapped time period and they can take it in so many directions due to the rough and tumble way people lived back then. It was in fact this idea of the Old West that makes Marston so unique; his sense of morals making him a very rememberable character.
So where does Rockstar go from here? Well I think the first step is to center it around totally new and never before seen character again. This gives the writing complete freedom because they arent tied down by the previous title(s). I also think that the idea of giving a factual place a fictional setting (Old West= real, New Austin= not real) is both good and bad. It is good because, once again, it gives the writers alot more creative control. However everyone like so see real places adapted into a video game (ie: Modern Warfare 2's "Holy Sh*t they just blew up the White House!" kind of scene). So they can do either and it will come off great.
As far as plot the idea of revenge/redemption has been tackled rather magnificently twice in RDRevolver and RDRedemption in my opinion so they could very well create RDRevenge or RDRetribution or something of that nature. But then that might seem rather "samey" if you know what I mean. Unless Rockstar plans on making revenge a reccouring theme then I dont think that will be considered as an option.
I personally think that whoever posted the blog about RDRevolution as an option deserves a medal, as that is a very original idea. However I don't like the idea of the main character being a Mexican. It's not that I'm racist, one of my best freinds is Mexican, and he and I both agree that that would be changing the game too much. For the past two volumes the main character has been of European origins and that seems to work very well. Redemption also portrayed it's Mexican characters in a very negative light, like the leader of the revolution ending up being a tyrant himself. That said the idea of the main character assisting in a revolution isn't a bad idea.
All in all this is nothing more than speculation and opinions. Be it so that you agree or disagree comment any suggestions or ideas that you may have. Who knows, maybe good ole Rockstar may end up reading the blogs on this site for ideas.