The Xperia 5 IV has not joined the Xperia 1 IV yet, but it could debut over the summer. While Sony France has refused to deny the former's existence, an unfortunate Sony Xperia Instagram post has intrigued fans as to the Xperia 5 IV's whereabouts.
https://www.notebookcheck.net/Sony-refuses-to-deny-Xperia-5-IV-existence-as-possible-typo-gets-fans-talking.625709.0.html
From the french video, the Sony manager does not "refuse to deny" 5 IV, he brings the subject by himself without even being asked about 5 series and suggest its release later. Cool !