Panasonic sent an email to one of their distribution lists with the subject line "Preview LUMIX S at CES 2019":
It is possible that Panasonic will officially announce their new Lumix S1/S1R full-frame mirrorless cameras at the 2019 CES show that starts next week in Las Vegas.
Update: Panasonic has a CES press conference on January 7, 2019, 10:00am - 10:45am PST