The Sony 100-400 is a great landscape and travel telephoto - probably the best out there. It covers pretty much the entire telephoto range in a single lens, and, critically for landscape use, is sharp corner-to-corner throughout this range. It even holds a 1.4x TC well on a 42MP sensor. The only thing I wish they could change would be to extend the bottom end to 80mm or so, to reduce the gap between it and the 24-70 (either that, or release a new, better 70-200, and then a 200-500mm). But it would be a secondary wildlife lens at best - backup for a longer, faster lens.
But probably the one thing Sony can do that would put it over the edge for wildlife photography isn't even a lens - it's firmware. Eye detection is AI-based image recognition. It's great for ensuring focus right on the eye, not on the nose, eyelashes, ear or some other part of the face. But, so far, it only works on humans, as well as some other primates (the A7r2, at least, recognised monkey eyes, but obviously not monkey faces). There shouldn't be any reason this couldn't be extended and further developed to recognise and track animal eyes and faces, or even inanimate objects. After all, it's the same image recognition technology being used and developed for autonomous cars, security systems and cruise missiles.
Long lenses will come with time. But taking advantage of real-time sensor data and using AI to improve focus and tracking could really put Sony bodies ahead of the others, whose mirror-based approaches don't give them nearly as much data to work with.