Without the MGU-H "mufflers" they will already sound 10x better than they do now. Add to that a little more RPM and you have screaming engines again. But i do not know how they will manage less fuel with that.
I think we have to hear them first before we judge
PS the current F1 engines have the best thermo dynamical efficiency of any combustion based engine ever achieved. It is interesting from an engineering point of view. But totally unworkable for road going engines and ridiculously expensive to develop.
F1 needs to develop technology they can sell to the automotive industry.
EDIT; To achieve higher RPM, the max fuel flow will be increased by 20%. Right now engines are capped to 11.500rpm due to fuel flow limitations. But at the same time more restrictive oeverall fuel consumption rules are proposed.
I say ditch the total amount of fuel caps. And let them race. It is in the teams best interest anyway to use less fuel. Less fuel equals less weight to carry at the start of a race. Less tire degradation and faster lap times. No external cap needed IMO.