As suspected, Kispal es a Borz is the Hungarian band that's set to say goodbye to their fans on the -1 day of this year's Sziget Festival. This is confirmed on the official Hungarian site. Kispal es a Borz is a very successful Hungarian band, that has over 20 years of activity behind it.
Superbutt are one of the most famous Hungarian bands of the moment, and they are confirmed to play at this year's Sziget Festival on August 14. The date is confirmed on their official website (thanks, Required). They've played Sziget last year, too.