I think he's going to change roles and become an amazingly effective political operative getting his choice of people elected. That could have a larger long term impact than another term as president.
@carpediem I think you are correct. If he runs for President again we will just have another eruption of Socialist hysteria, and fascist riots, as we did during his Presidency. When Pelosi and Schumer are dead of old age, (may that day come very, very soon, please), the real radicals will take over, and the Republicans can't concentrate on ONE person to save their party.