It turns out that our own Damien McFerran is Build-A-Bear Bonus Club member, even though he doesn't know how, and along with other members got a heads up on another Pokémon joining the range this week.
It's fire-type Scorbunny, a recent addition to the franchise in Pokémon Sword & Shield as one of its starters. It arrives online and in UK stores tomorrow (6th May) at 3pm UK time, with ScorbunnyTomorrow:UK:20210505:All%20Subscribers">this page of other Pokémon toys a good bet for where it'll end up. It'll be worth keeping an eye out on your regional Build-A-Bear websites and stores to see if they also add the 'Rabbit Pokémon'.
There's no extravagant waiting list setup planned, it seems, so this is unlikely to be a launch with the madness that accompanied the Animal Crossing range. In any case, is this one you want to add to the collection?