I had a drowned farm set up a few months ago, and tridents were dropping like crazy.  I quit playing to wait for the update.  Now the Nether update is here, and I have started a Realm with my friends.  We have a zombie spawner set up the EXACT same way as the previous world, but even after two days of non-stop grinding, not a SINGLE trident has dropped.  

Additionally, Iron Swords and Iron armor doesn't drop nearly as often as it did.  The most common drops now are Gold bars, Gold Armor, and Rotten Flesh.  

We tried to get tridents the natural way as our world spawn is near the ocean.  After a week of that, we only got 2 tridents.