Thre is a newly published patent application describing the specs of a new Olympus 400mm f/4.0 lens. It’s unclear if this lens will be produced at all.
I don’t knwo how reliable this source is but months ago OzRay reported on Dpreview forum:
After years of planning, development and testing, Olympus is considering cancelling the production of a 400mm f4 lens. This lens was going to be one of the most superlative lenses ever made by Olympus; however, after extensive surveying, it was discovered that it might only meet the needs of a very small minority.
I think the 400mm f/4.0 lens would be amazing for wildlife shooters!