I believe Netanyahu is in three positions ... He is a member of the Knesset, he is the head of his party, Likud ... and ... he is Prime Minister.
SO, he might not be Prime Minister any longer (but we’ll see). Also, if he loses, the Likud may be mad enough at him that he might not be head of his party. At the end, though, he is a member of the Knesset.
i believe Bibi has said he would resign as head of Likud at 18 seats or fewer.