Looking at the 80-200 f/2.8 vs. the new 70-200 f/4, I would expect the new design and coatings to be better in terms of image quality, but the loss of a stop is another thing.
The area where some older lenses may still outperform new lenses would be some top of the line primes. Some of the older prime lenses are known for fabulous image quality. Where they may fall down is the lack of coatings to manage reflections and chromatic aberration.
While there are some very good DX lenses - and some real bargains - most are designed for a specific price point with compromises as needed to keep cost down. It would be great to see some new high quality DX lenses.