I've been a reader of this site for about 7 years, but never made an account. I just did, just to reply to your comment. Um.. do you realize that Nikon's 500 5.6 pf has been getting sold like crazy since it's release? I really don't think you understand just how amazing a 3k 500 5.6 is.. "perhaps canon knows something you don't"... While implying a 500 5.6 won't sell? Thats a little bit delusional. The 500 pf, 200-500, and now the 400 4.5 which overlap each other still exist because Nikon gives option to us mere mortals that can't buy a 10k lens. Canon's 100-400 ii is amazing but no it's not at the level of the 500pf (of course it's cheaper), neither is the 100-500 which is f7.1 and not quite as sharp.. anyway.. its very obvious why canon hasnt released a 500 5.6. it would be too affordable and people wont buy the 400 do.
Also you said "..... Personally want something"..SO MANY people have been asking for an update to the now *30* year old 400 5.6, and the 25 year old 300 f4. Canon hasn't even bothered. Cmon. In 30 years they couldve updated it twice. Again, the reason behind it is very clear.