SNI is the "server_name" extension in the ClientHello message, which is not encrypted. So no, looks like there are no changes to this in TLS 1.3. Theoretically

SNI is the "server_name" extension in the ClientHello message, which is not encrypted. So no, looks like there are no changes to this in TLS 1.3. Theoretically it could be possible to encrypt it (using DHE) before server validation occurs (i.e. before the server's RSA certificate is needed). However, it would rigorously change the protocol and I can imagine it would make some load balancing applications a lot more complicated as well.