No, there are none from WotC.
When Crawford, Mearls and Perkins were asked about it the consensus was that after level 15 the game is mature enough that the DM can build on whatever has already happened. Moreover, few games last long enough to get much beyond level 15 or 16 for real life reasons.
Real life reasons (at request of the asker)
Getting to level 20 takes a long time, and things happen in players lives. They get busy and can't play, their characters may die, want to play other games, etc. Each of these can slow down or end a campaign.
As a result WotC doesn't see much demand for adventures over level 15 in surveys they write. Also they want evil to win.
Drawbacks to level 20?
There are no drawbacks. You can run your own adventures or you can use published material for lower levels by scaling the adventure using the scaling monsters rules from the DMG.
Moreover, play can go beyond level 20, the DMG just offers that can continue to earn epic boons, but they don't give much information on epic level games/gaming. There are a host of different homebrews for post 20 leveling.
It could be argued that at level 20 or beyond that you've so outgrown the world that a lot of players might find it boring -- but there are still more challenging monsters. The Tarrasque has a challenge rating of 30, but there is nothing stopping a DM from creating creatures above that in their worlds.