If Rosalie Craig wasn't deemed essential I can't imagine Jonny Bailey being brought over. (As I've said on this board before, I loved him in the show and for me he was the best thing about it.)
I hope he continues doing theatre as his star power increases. I saw him in the wonderful play The York Realist at the Donmar and he is a remarkably open and vulnerable actor, especially for someone who has such devilishly charming looks. He was also very funny as the snarky BBC junior producer in WC1 on BBC (of course).
Wish I could see Cock but hopefully it's a sign he intends to keep his stage chops sharp.
(And that YouTube clip of him trying out for The Last Five Years is mesmerising.)