Hopefully, when released these will be easier to get then the 400mm f/2.8 GM.
Not likely to be announced during the 2019 NABShow although, SONY is making an announcement today at 2:oo pm PST
From Alpha Rumors
https://www.sonyalpharumors.com/new-sony-patent-discloses-500-f-4-and-600-f-4-e-mount-lens-design/