Assuming growth rates of 3.3%, per capita world GDP will be $200,000. American per capita GDP will be one million. (See Alex Tabarrok's optimistic video here.)
So often, politicians talk about saddling our grandkids with debt as if they'll have to find jobs when they still can't find their shoes. They'll grow up, become smart, and perhaps wildly productive. They may well be making an average of one million per year.
With numbers like that, I think that the grandkids can service trillions of dollars in debt.