He's gone.
Most likely candidates are John Swinney (if he goes for it) and Kate Forbes.
Swinney has all the charisma of a plank of wood, he's been leader of the SNP before and wasn't very good at it, nor has he been all that succesful as a minister.
About the only thing you can say about him is that he's the safe choice and the Greens are more likely to accept him.
Kate Forbes won't be accepted by the Greens. She's a West Coaster and much more socially conservative, but she was reasonably successful as Finance Minister. However, she lacks long term experience.
Mike.