Some time ago, Dave asked the question - why so much used Creedmoor stuff for sale.
I've noticed the same thing, a lot of 6.5 Creedmoor stuff. Dies, rifles, etc.
I don't think it's a decline in popularity of Creedmoor in general, I think we're seeing the first crop of shooters who bought the 6.5 rifles, shot them out, and are moving to 6mm.
The general trend in the Creedmoor is now 6mm, so that would explain the selling of dies as well, people are just moving to 6mm Creedmoor.