On September 5, Dr. Mario World will welcome a content update that features a new 20-stage world and Dr. Baby Mario. The game will enter maintenance mode on September 4 to make way for it, then you’ll have the chance to continue your adventure/unlock a new character respectively.
Dr. Mario World launched in July, and saw a similar August update that brought a new mountain-themed world and Dr. Daisy into the fray. The whole free “world + character” concept seems here to stay for the foreseeable future.
I occasionally still boot up World to keep up with it, but don’t play it regularly due to how busy the UI is and fact that I get advertised to constantly with “buy crystals!” popups. I own various incarnations of Dr. Mario 10 times over, so I may as well play those: my current go-to is Dr. Luigi.
In-game notices [Dr. Mario World via Perfectly Nintendo]
Source: Destructoid Dr. Mario World is getting a new zone and Dr. Baby Mario this week