Nintendo confirms Switch OLED Joy-Con are the same as current controllers
In a brief FAQ posted on its website, Nintendo has confirmed that the Joy-Con included with the new Switch OLED will be the same as current controllers. That means any Joy-Con you have now will work with the updated console.
Also worth mentioning, every Switch dock is compatible with all Switch models. If you want to use the dock that ships with the OLED version with a regular Switch, that will work (and vice versa). However, an update may be required.
The FAQ also mentions something regarding Nintendo Labo. It states that “there may be differences in game experience with some of the Toy-Con accessories from the Nintendo Labo series, due to differences in console and screen size between Nintendo Switch (OLED model) and Nintendo Switch. There may also be games where the game experience may differ due to the new capabilities of the console, such as the larger screen size.”