Peeking around the official forums, I saw a few threads dedicated to the reincarnation of 40-man raids. Do you remember the old, pre-BC epic AQ-40/MC/Naxx days? I can honestly say I really do not. I was a freshly minted 60 when BC came out. I got my feet wet in ZG and AQ-20, but that's it. Perhaps I'm missing out on something important. It's entirely possible that others feel the same way.
Since Blizzard has tuned Wrath raids to both 10 and 25 person versions, what's stopping them from rounding it out to a full 40. Perhaps they could even go for more. Many are already complaining that Naxx is too easy. They're looking for a real challenge. I don't know if Blizzard is open to the possibility of tuning up the dungeons, but we've seen evidence that the developers do listen to player feedback.