I stand corrected. I also found Emrax 268 which has a power to weight ratio of 10 kW/kg. But these are good only for small aircraft. It's much harder to maintain this power-to-weight ratio for larger motors. Emrax 268 is only 20kg, but a single engine of 777 weighs 8200kg. The ballpark for large motors at powerplants is currenly around 1 kW/kg [1]. But who knows; there might be a breakthrough in motors too.
You can stack Emrax motors on a shaft. Also, the technology scales up in diameter. Not that you really want _that_ large props necessarily, if you can get away with smaller ones. This combination should be enough, I guess.
Edit: I think I met the guy behind these. But I'm not sure, for lack of having asked for the name of the company. I certainly have seen a prototype that could have been the 348.
Generally you should prefer few large propellers over many small ones due to aerodynamic efficiency. Stacking up motors axially sounds like a very good idea though.
[1] https://newatlas.com/siemens-world-record-electric-motor-air...