Joe Stange's got a major piece on session beer coming out in DRAFT magazine this summer; can't wait to see it...especially in light of this new post on his blog, Thirsty Pilgrim. He throws cold water on the whole idea that session beer is trending upward in the U.S., citing ratebeer.com data on new beer introductions over the past ten years.
However...I'd suggest that you don't look at session beer the same way you look at extreme beer. Session sells by volume, extreme sells by margin. As I commented at his post, Yards sells over 50% of their total output at 4.5% or below...but that's only two brands doing all that volume. Perspective. We'll see; in the meantime, good to have a reality check.