I think the one factor that almost every blogger who has weighed in on the topic has missed is that people raid for easy top-quality loot. Likewise, people do a daily heroic random for their Frost badges, again for easy top-quality loot. Back in BC, people flowed into arenas, once again, for easy top-quality loot. Loot is a tool, a reward offered from Blizzard to get the playerbase to enjoy the game in the manner that they are putting the most effort into. People (and by people I mean the overwhelming majority of the endgame playerbase) will swarm to the easiest way to get their top-quality loot, to the best of their abilities.
If Blizzard wants to kill 25-man, they're welcome to do so, it's their game after all. Shifting the effort-to-loot balance towards 10-man is a sure way to do it. I, for one, don't think we'll see quite the abandonment of 25-man as is being feared... all it takes is one legendary item that only can be earned in 25-man and all the top-tier raiding guilds will jump on that like a puppy on an unattended turkey sandwich.
Not all the information is out. Don't start making plans to dump 60% of your raid core just yet. Blizz may yet surprise us.
Being paid for playing games
2 days ago