The Sony a9 II is already confirmed to be announced in mid or late October, 2019, just ahead of PhotoPlus EXPO on October 24th-26th. According to recently rumors, Sony a9 II could use IMX435 sensor or IMX311 sensor.
IMX311
Sony New CMOS Sensors Leaked: IMX311, IMX313, IMX409, IMX521, IMX554
A new series of Sony full frame CMOS sensors now leaked on the web. These image sensors are all full frame sensors: IMX311, IMX313, IMX409, IMX521, IMX554.