They showcased cards in multiple languages over the past 30 years, but not the actual cards from the set. So my guess is there will be a new gimmick that allows the set to feature illustrations from the past but will still be treated as brand new cards
- Think back to SM6a Champion Road, which brought back cards from Neo to ex era but with the updated Sun & Moon format
Or, the most tame assumption is that this could be a small set with Mew and Mewtwo as the chase mascots of Celebration Collection (Mew was the chase of 25th Anniversary Collection). Card outlines teased in the visual should at least mean there will be Mew ex and Mewtwo ex