AW had Korea with jets, p51s etc. It was empty most of the time. I flew it several times and it was a blast but the arena seldom had over 10 people in it at a time. I don't think there has been a successful Vietnam era flyer nor has there been a successful mass online jet game. Several have been on but they haven't lasted.
As far as WW1. If its done well the people will play it. I like WW1 so I would probably play it a lot. I left AH before to go to WB just for the WW1 game. But after awhile I left because there really were only a couple of decent planes in their plane set. The only planes that flew decent was the Fokker Dr1 and the Camel. The Fokker D7 was a dog there and it was supposed to be one of the best planes of WW1. Apparently using the same WW2 engine didn't cross over too well. It was fun but extremely limited. Now if AH builds a comprehensive game with flyable zepps, bombers, and maybe even some WW1 tanks it might be interesting. WW1 (and most other eras) depends on the game play though, to much reality and it bogs down, too little and its an arcade game.
For me the deciding factor irregardless of the era would be how good the game play is.
