No one does this more than Doo. Poo did it last year with the Terrain Dominator - it was really a mid-season release. These are sleds that are available to buy, not just test - my qualifier.
Cat already did it this year with the XC 6000 race sled, a hardened and more expensive version of the 6000RR (peeps who ordered the RR last spring got abit of a hosejob on this one). They are selling the XC race version at select dealers now, no resume required. And Doo just did it with the Iron Dog MXZ with the 128 track. I can't come up with one that Yammy has ever done (when they were all made in Japland).
With that said, I don't think there will be any mid-season this year from Poo - it would take away from the excitement about the Axys RMK announcement for 16, and they won't be delivering a production Axys RMK until next fall. They could have an Axys short track mid-season release, but I doubt it, since the Pro-S's are not sold out. Think this will be a quiet mid-season for Poo. Then the Axys RMK will be official, with limited models available to test at dealers this spring, just like the Pro RMK was intro'ed in 2010. That sold them truckloads of 11 RMKs - they'll do this again. JMHO.