In the next update for Minecraft on Nintendo Switch, the team has announced that players will be able to transfer their worlds from their Wii U systems onto Switch. The main loading menu in the game will have a new save option that will allow you to transfer save-data to your Nintendo Switch console. Similar to how Airdrop works on iOS, both consoles must accept the save-data transfer in order to do so.
The transfer-save data option was meant to be available at launch, however, the team decided that they needed more time to work on it.
Source: Nintendo Everything
