I asked the lady at the counter once if they were going to be switching up the fillings or if those were the only ones they were offering, and she said since it's a new product she's not sure yet if they'll be having new flavours or not. But since they didn't have bison that one time I checked, that probably means they're rotating the flavours like with the soups
You can always drop in and ask them! maybe they have a printed schedule or something.
Also, they sell them in the food area in IAHS as well! (although, that place closes early too).