Yes, I imagine this too.
The U.K. and Canada have always been primary markets for Apple, then Australia and New Zealand. Everywhere else always seems to come later.
I also believe that Apple Cash will launch anywhere the card launches - it might be at lower rates than elsewhere, but cashback at the Apple Store is a definite feature of the card, I would suggest, even if provided at a slight loss to encourage overall usage.
They will also want to be launching in markets where card usage is high, so I would be surprised if the U.K. isn’t high up the list.