I hope some developer shows off a 4k 120fps game. At the very least I want to see 1440p 120fps out of a console. Will get me somewhat excited for Xbox's future and may make me more interested in it.
On the other hand, I hope if devs are targeting 4k/60/120 or whatever that the PC games will also rise as well in performance. The old saying a rising tide lifts all boats.
Edit: Ubisoft confirmed on Twitter they will be attending the event with Gameplay of AC: Valhalla.
They've already talked about hitting this target so it's not even unrealistic. Not sure why the sarcasm? All I'm asking is to see some developer actually reach those claims.