I Guess it depends on what new hybrid... that Tahoe hybrid is not really impressive. I hear that the next gen Toyota hybrids will get around 90mpg.
As far as the Math goes it will probably get to be a better deal once used hybrids start to come into the market more.
One thing that was not mentioned, if my memory serves me correct, was that you get a substantial tax credit with the purchase of a hybrid so it may be a better buy.