I stopped by Once Upon A Toy in Disney Springs hoping for a surprise parks collection release. However, the store still had the Lion King sets along with a selection of standard Tsum Tsums. They had some Marvel characters left by the counter, mainly Black Widow.
One of the sweet Cast Members I spoke with, told me that they only receive new collections about once a month and that they have no prior knowledge of when it will arrive. She said that typically new Tsum Tsums show up mid-month, but the Cast Members are just as surprised as we are.
Check back here mid-month for an update. In the meantime keep an eye on DisneyStore.com in the shop Disney Parks Section for any special park sets.