Ricctalks mentioned the IQ of the 100-400 S is very similar to the 180-400 f4E TC14, which is impressive at its price. The arrival of this new zoom has upturned my carefully planned wildlife system...(even though I'd traded in a 80-400 G in June for a decent price). Anyway, previously I'd been trying to work out how to save for a Used 180-400 f4E TC14; so this new Z-mount zoom is affordable (in comparison) and it should tick most of my needs, except being slower, especially with a TC, and yes it lacks the Internal TC and zooming.
On a more strategic note, looking back over the past few years - since August 2018 - Nikon has strengthened its position in leaps and bounds with the supreme status of their Z mount ie 16mm throat and 54 wide, and 94+ F Nikkors and the new system of 26 Z optics (and counting....). It's unlikely coincidental how they rolled out the sequence of 70-200 f2.8E FL, 180-400 f4 TC, then 120-300 f2.8E SR (2017, 2018 then late 2019). All considered, these have overhauled the status of the tele zoom compared to the best primes! Since then we have seen the sequence of Z mount S zooms (late 2018/2019: each is excellent).
Considering the 300 f4 PF (2014) and then 500 f5.6 PF (2018) in analogous context, it will be interesting to see how Nikon design the 400 PF and 800 PF
(Phase Fresnel is assumed on their relatively shorter silhouettes). Both will be interesting, particularly how the roadmapped 400 S PF relates in IQ to the 100-400 S. Subject to final size, speed and price, I am eyeing the 800 prime with much interest, because I often have the TC2 III on my 400 f2.8E FL.