As far as I can tell this is going to be a free update. The only charge will be for people who want to “upgrade” to the Switch 2 version.

A small list of inclusions:
-Zelda/Lego/Splatoon crossover characters, items
-A hotel for villagers to stay in while they come visit
-Slumber Island - ability to create new islands (up to 3) without getting rid of your main island. Accessed by going to sleep
-Crafting multiple items at once