And the governor is currently in a primary fight with Ken Bennett, who has made McCain's successor a campaign issue. So if McCain resigns and Ducey appoints another McCain, he's toast in the August primary, and he's not doing too well anyway (see below link).
So look for McConnell pressuring McCain to come up with some other acceptable appointment other than his wife or daughter, so he can resign and McConnell will have another vote in the senate.
Stubborn, selfish oligarch McCain!
What’s taking so long?