400 cards and 31 kingdom piles. If they're all normal-sized non-Victory piles, that would account for 343 cards, leaving 57. I'm guessing that Allies are some kind of non-supply card. It could be a single kind of card, like Horses in Menagerie, but I'm gonna guess that there's different kinds of Allies, with probably 10 of each. So, maybe 4 different kinds of Allies, leaving 17 cards for Events or some other landscape? Of course, there could also be one or two Victory card piles, or a pile that has more than 10 cards like Port and Rats
My prediction for the rotating split piles: they're one-shot cards that work like Experiment or Horse where they return to their pile, except that instead of returning to the top of the pile, they return to the bottom. So, they might start out like a normal split pile, 5 copies of card A on top of 5 copies of card B. You buy a copy of card A, and now it's 4 of A on top of 5 of B, but then you play your copy of A, and it goes to the bottom of the pile, so now you have 4 of A on top of 5 of B on top of 1 of A, and so on. Or maybe it's more like Castles or Knights where each card is different, but probably not that, since it says piles, plural, and that would mean that there'd have to be at least 20 different cards