Well Diplomacy did add faster settings for things like resource income rate, build times etc. I don't think Rebellion increased those further, but there are new victory modes that can seriously speed up games if they are enabled. The flagship (a player loses if his flagship frigate he starts with is destroyed) and capital (a player is eliminated with their homeworld) makes it so you don't have to stomp out every planet to kill a player. There is also an occupation (take a heavily fortified planet in another star system and hold it long enough to win) and research victory that allow you to instantly win and defeat all players, but they are fairly difficult to achieve but can reduce the amount of time it takes to win very large games by a good margin.
Sadly from what I understand the multiplayer comunity isn't really using these modes yet, and against the AI games can still take a while (not the least because its getting a lot better). But if you're mainly interested in single player there will be a mod that will speed things up I think. 
So I would say its definitely not a very fast and click fest oriented game like starcraft II, but it can be a lot faster than Sins used to be depending on which settings you play on and your play style.
