Apologies if done, but I'm surprised to see no discussion about it.
The Redbull DH WC coverage on the weekend suggested everyone was on 650b already except Santa Cruz Syndicate and Specialized. Gwin appeared to be using a 26" Spesh Enduro frame with triple clamps.
I don't know much about DH beyond the coverage though, but that SA course is supposed to faster, less technical, and more pedally than the rest of the courses even after they made it hard enough to ensure triple clamps were needed.
Has 650b really come on this quick, or was it just for this course?
I've suggested on previous threads that I thought 650b would take over for DH, but I didn't expect it to be quite this quick. I thought they'd need another off season to practice with all the equipment such as tyres being more widely available.