So there's still 1 Detective Pikachu card yet to be revealed...The official website states there are 27 cards yet we currently have 26 (18 from the set + 3 GX promos + 2 Detective Pikachu promos + 3 in-store event promos). Must be a special Pokémon, possibly Mew.
Some of the products for the Japanese set have been revealed and the 3 GXs were revealed. Based on their card numbers in the set, their set of 24 consists of our 18 + 3 GXs + 3 in-store event promos. Although the Detective Pikachu in their set is our promo 'Brilliant Deduction' one. The products revealed 2 Detective Pikachu promo cards, one is the 'Scout' one that is in our set, and the other is a brand new one (which will no doubt be our promo SM170 in the Figure Collection). So that's all 26 cards as well. Their set did say 24 + ???, so perhaps it means that this unrevealed 27th card will be a secret rare in the Japan set? Otherwise what a tease to have the "+ ???" but turns out there were no secrets and it is just 24.