1. ... Apple TV does not plug directly into an HDMI port without a cable and requires a traditional power outlet. ...
2. I am completely over the touch surface remote control. ...
...It's been reduced to a benign component of my HomePod/Apple Music experience and the twice-a-year "let's watch home movies, dad" moment.
Maybe it's time for ... ATV Air and ATV Pro?
I don't see the dongle format as having the power for higher-end use of serious games or high-load video. Doubt it's going to fit quite so well as implied behind many TVs, and powering from random USB ports is unreliable (and commandeers that port vs other use). Yes, it might be sufficient for most users, but with distinct limitations which can become glaringly apparent (something Apple wants to avoid).
So...maybe we will see a ATV5 Air as a dongle. Just need a way to pleasantly delineate its limitations vs the more powerful "puck" format.
An ATV5 Pro would likely remain a "puck", but I don't see what would really be advanced beyond ATV4K other than using better chips simply because they're current and in large supply (at Apple).
Such a divergence might be delayed until 8K video becomes a widespread[ing] thing, as that will require heftier hardware not necessary for those content with 2K or 4K video which might be handled in a dongle-sized-and-powered device.
...and that stage will require a pervasive update throughout the Apple ecosystem, as hefty hardware for creating & distributing 8K is needed before distilling it down to something easily handled by a sub-$200 device.