I'm really glad I got in that post on Variable Group Size instead of sitting on it for a while like I normally do.
So Blizzard is introducing Flexible Raids, which can have 10 to 25 players and scale in difficulty. This will be interesting to see. I think it will be a success, but I also think it will end up cannibalizing Normal mode raiding. Removing modes is never very popular, but I can see the next expac having Raid Finder, Flexible Raids (with a slight difficulty increase at the top end) and Heroic Raiding (with a slight difficulty decrease at the bottom end.
I think the administrative advantages of Flexible Raids will prove to be too tempting for Normal Mode guilds. After all, a Normal Mode guild has all the headaches of Heroic Raid roster management, but lesser gear and lesser prestige than Heroics. Another small step down is not much compared to not having to worry about rosters.
Flexible Raids will use the Raid Finder loot system. I think that's pretty good, because it scales. To be honest, I think if Blizzard announced loot being won to everyone in the group, people would be happier with the loot system. There would be tangible evidence that someone is getting loot whenever a boss dies, and it's not just you getting gold all the time. Plus you could congratulate others when they get lucky, and they could congratulate you. Bosses would feel more rewarding because you would see that someone in your group won something and the group became stronger.
I also see a lot of chatter that everyone will be "forced" to do Flexible Raids. Since it has its own gear level, I don't think much of this concern. If people insist on killing themselves for lower quality gear, maybe it's time to just let them go their own way. I do think that a lot of this concern would be mitigated if Blizzard overlapped some of the item levels between tiers (the way The Old Republic does). That way people would already have upgrades from the previous tiers.
All in all, Flexible Raids a big step forward for PvE MMOs. Blizzard continues to raise the bar. It will be interesting to see how other upcoming MMOs (*cough* Wildstar *cough*) respond.