It's the model meant to be on sale at the start of 2016 rather than put into production for the 2016 selling season.
Similar to how the 2016 model auto selling season will start in September/October after the August factory retool. In RV's this starts in May or June. Any way its just marketing. After all you wouldn't want to buy a 2015 model now, in 2015.
Would you?