I don't expect the 5D4 to compete so aggressively in the AF battle. I think the single Digic will really tie the hands of it when it comes to AF tracking, much like the 5D3 was underpowered the same way.

I agree that the 5D4 fits in between in certain ways - it'll be our next camera purchase as it's a good upgrade for my wife's 5D3 and a good backup for my 5DsR (without buying another 5DsR "just" as a backup).