" Nintendo Switch controllers can be used wirelessly and are also compatible with Nintendo Switch 2 exclusive games, but cannot be used if the games requires features unique to Joy-Con 2, such as mouse controls." Nintendo also mentions how some other features on these older controllers won't be available on the Switch 2:

Nintendo has confirmed that the existing GameCube controllers that are on the market are still compatible with the upcoming Nintendo Switch 2.

GameCube Nintendo Classics are exclusive to Switch 2, and you'll need a subscription to buy the wireless GameCube controller.

When moving from one generation of consoles to another, it’s not always guaranteed that old accessories will work with the new system. So, do old Joy-Con, Pro Controllers, and other accessories

Here is a detailed guide stating the compatibility of Nintendo Switch 2 accessories with those of Switch 1 along with a few exceptions.

Nintendo Switch 2 will have access to GameCube games exclusively via the Nintendo Switch Online service, including The Legend of Zelda: Wind Waker.

According to podcaster 'Nate the Hate', who previously revealed Game Boy and Nintendo 64 updates for the Switch Online service, he now appears to be teasing GameCube for Nintendo's subscription service in possibly the first year of the Switch 2's life.

Nintendo just dropped a boatload of Switch 2 news, including the release date, price and a launch title or two. It also announced a bevy of accessories that’ll be available for the console on June 5.