Is there still a market for ports and sherries (dessert wines/apertifis) or not?

The cheap ports and sherries are everywhere (grocery stores, liquor stores, etc.). Wine stores carry both, including very expensive vintage ports meant for aging. Most fine dining restaurants carry port (usually by the glass) more so than sherry. Though plenty have sherry as well.

Dessert wines are an acquired taste, but will always have a market. Since many sherries aren't sweet and there is a wide range of very interesting ones, I could see some big resurgence at some point.

If they are still being sold in liquor stores, there is still a market for them because NO ONE stocks stuff that doesn't sell. call your local liquor store and ask them. A lot of stuff like that can also be more regional too.

It's not the size of the market but its exclusiveness.