Yeah, it will have to be his health at this point. We have some nice foreshadowing with the prominent stroke droop, recent bizarre capture of his eyes falling out of sync, and chronic ear infections. In a normal person, these things would be canaries in the coal mine for brewing issues.
Realistically, the bankruptcy should have been it. If anyone had been competent, if anyone had done their job, and if there weren't a pandemic muddling things, Phil should have been absolutely destroyed, and it would have been public by nature of the proceedings. People were bitter about it because it really was the logical narrative conclusion. But it didn't happen.
Now we linger on in real life 'overtime', to put it in autistic stream schedule terms, and it's become abundantly apparent that only an act of God is going to strike Phil down. Otherwise, he'll just meander in this holding pattern of misery and failure, probably banking on his inheritance as any sort of retirement plan. The finale is going to have to come from within, as his own body fails him in a final grand act of detracting, if it is going to happen at all.
He may outlast us all. But at least he'll hate every moment of it.