The future of economy class seats - GIF

[ductape]

The front of the step runs have yellow strips. It's a quick pan and kind of hard to see.
The upper seating areas have a couple of steps, which is a potential violation of US ADA law unless the airlines using this system want their employees to lift some passengers in and out of those seats. There are lawyers who make a living from these type of lawsuits. Not sure about the rules in other countries.
The carry-on compartments above the seats in some aircraft would have to be removed in order to make room, so more checked baggage. Extra bonus.
Current US FAA rules require that passengers are able to evacuate a commercial aircraft in 90 seconds. It's unlikely now and certainly won't happen with this setup.