I photograph birds
Would any of these interest you?
I am interested in the 50-250mm f/4. If it is less than 1 kg, weather sealed, and around $1K USD, that would be my future birding lens. (In other words, less expensive, smaller, lighter than the 100-400mm f/5-6.3) Not sure if that is realistic. A nice to have would be TC compatibility, but I think I can get by with 500mm equivalent FOV.