Ryanair have now loaded S19, not sure if it's complete.
So far I've noticed 1. Carcassonne ends next month and doesn't come back. 2. Hahn ends at the end of W18. 3. Berlin, which transfers from Glasgow at the start of W18 seems to disappear at the end of the winter. 4. Seville only operates this winter.
Some other routes which started in W17 are suspended this winter but restart for S19.
I'm sure others will find other changes.