With a lot of companies, they have the new model changes in December and January, but sometimes will make midyear changes to the line to spice things up.
Last year was the introduction of two Moto-Massage DX jets in the Grandee. This year they added a water feature to the Tiger River Bengal.
The mid-year changes are generally pretty well-known by the time they happen, but the new model year stuff is hard to get info on, and it ruins the surprise.