It depends on what you mean by tax increases. You can get a tax increase out of top income people by raising the rate, or you can get a tax increase by broadening the base. I have stronger views about broadening the base than I do about increasing the rates. There's plenty of room for broadening the base at the top income level.
That was my proposal for reducing the preferential treatment of capital gains. It was essentially to broaden the base and get more revenue from people who are converting other forms of income into capital gains simply in order to get a tax break.