You slightly miss the point. Warren Buffett has established a seperate Charitable Trust for each of his children to run. He has $billions in stock that has appreciated considerably over the years and he has never paid tax on any of it because he never sold it.
He will now donate the stock to his children's charitable trust, and Bill Gates's Charitable Trust, and take a tax deduction for the Full Current Value of the stock, then his children will sell it and because they are a charity, they will never pay tax. You notice he never proposes a limit on Charitable contributions.