How will this work in Revolution if there is a cap of 4 players? 2v2? 3v1? Doesn't really seem like it will be important or even exist. In this respect.

I could not even begin to answer that as the diplomacy system was hiccuping (yes, that is the technical term ;)) at the time I previewed the game earlier this month. (Only saw a brief exchange in single player in a demonstration.)

So far my only problem with Civ Revolution is the player cap of 4 players :/

It just doesn't seem like enough people to have a game that is impacted significantly by diplomacy. Also, this kind of limits games to just Pangaea type maps because the continent combinations are few, and having 2 per continent, or 3 on 1, 1 on another, or 2, 1, and 1, isn't very appetizing (to me). Islands won't suffer at all of course.

I think that Firaxis should've planned for cap of at least 8 players if they want all the features to be experienced thoroughly. In normal civ multiplayer games, games that start with 4 players, usually 1 falls within a few minutes (rushing), that leaves you with 3, which isn't really that intense of a game...