A reader sent me this picture of the upcoming Olympus M.Zuiko Digital ED 150-400mm f/4.5 TC1.25x IS PRO lens that you should be able to use handheld at 2000mm. Reportedly this is the final production version which means the official announcement should be coming soon.
Update: the Olympus M.Zuiko Digital ED 150-400mm f/4.5 TC1.25x IS PRO lens should be released in Fall 2020.
The latest Olympus M.Zuiko Digital lens roadmap can be found here: