Back on topic, I do think that Cata will be the fall of 25man. Already you're seeing so many guilds focusing on 10man instead of 25man as compared to the start of WOTLK. There is no more hype to killing a boss in 25man anymore because everybody else is at the 10man progression thread. My guild which has been doing 25man from BC till the end of WOTLK is now only doing 10mans.