Porsche many years ago came to the conclusion that big bore, big displacement engines with few cylinders were impossible to balance correctly.
The 944 S had the biggest 4-cylinder engine in production at the time (3.0L) and it had an advanced counterbalancing system to try to minimize vibration, but it still vibrated more than their 6- and 8-cylinder ones.
The development of combustion engines has come to the end of the road. It's pointless and a waste to try to develop something in a 20 year perspective. It'll prob all be electric by then with some sort of turbine APU in hybrid setups.