15-man raiding is the option of last resort

Blizzard has made numerous comments over the past year that 15-man raiding seems like a good size compromise between 10-man and 25-man. The 15-person raid can provide enough slots for the necessary class balance, yet let flexibility come into play in exactly how many players of each class are taken.

While some players are keen to enter the era of 15-man raiding, others loath the roster moves and guild shakeups this would cause. For those that were not around during the 40-man to 25-man transition in The Burning Crusade, many many guilds fell apart over having to make drastic cuts from their rosters. In a series of tweets, Ghostcrawler notes that the transition to 15-man raiding would cause guilds to prune 10 people from a 25-man roster, however I'd contend it'd be much more than that (around 15 people would need to be cut), due to the fact most 25-man guilds carry several more folks than necessary, which wouldn't be needed in a leaner and meaner raiding crew.

However, it appears that a transition to 15-man raiding is essentially off the table. Ghostcrawler tweets:

Have players forgiven Blizzard for the social shakeup that came with WoW's first expansion? I'm not sure to be honest. Obviously many people agree that 10-man and 25-man raids are logistically much easier to get running, but the initial social cost of that jump was pretty high. Personally, I'm over the transition -- it happened long ago. But, it's clear that Blizzard learned their lesson about changing the social structure of the game so drastically; they don't want to do it again.

The 15-man raid being an option of last resort also puts a nail in the coffin of those that thought Ghostcrawler's "unannounced feature" was a conversion away from 10-man and 25-man raiding.