I'm not too sure. They need May just as much. Corbyn is just as likely to help his mates in SF to push for unification of Ireland, the DUP hate him just as much as the tories do.......
They will do a very loose deal, but May will have to drop most of her key policies. Corbyn is literally the only reason why they will keep the government alive. But it's not a workable situation long term, and they won't hesitate in blocking something they don't like. They are pragmatic tho when they want to be. They've struck deals with SF for 20 years. It definitely won't be anything close to a formal coalition tho. Deal by deal, issue by issue.