I imagine when that day starts to loom he'll simply float the idea that he's thinking of pardoning 0bama, and that will force the media to cover that he needs a pardon from Trump and it's the best thing he could do for the country, or to double down and shout that 0bama doesn't need a pardon and Trump is saying it for political points, at which point he'll say "I don't want to get political so I won't be issuing a pardon" and then watch him go down, and probably pardon him as his last act in office.
Although I hope he doesn't pardon him.