This is a most interesting discussion we should be having more frequently, I suggest a weekly or monthly column dedicated only to engine types and technology advances.
For me, give me a DOHC naturally aspirated high revving beauty any time of the day, no matter if it’s a 4-liter V8 or a 3-liter 6-pot or any i4 from 1 liter to 2 liter. I simply don’t like how a 6 or 7-liter pushrod V8 sounds, too truck-like for me. Torque is overrated, just downshift and hit that gas pedal to the ground, don’t be shy. If the vehicle is lightweight, you won’t need that much revving anyway, if a one-cylinder 200 cc motorcycle can accelerate up an overpass in fourth gear carrying all 155 pounds of yours truly, so can your 250hp sensible sedan.
Also, it shouldn’t matter if it’s turbocharged, if Formula One engines are turbocharged AND electrified and can revv up to 13,000 rpm I don’t see why car makers don’t make a 1.5 turbocharged i4 powering a light weight economy car with 180hp or so. It makes sense for me.
As for your criticism of 2-liter i4s, I believe 2 liters are a relatively high displacement for a four cylinder, that would explain why it can only revv to 6,500, excluding awesome 2-liters like the Subaru FA20 (7,400 redline on the BRZ and Toyota 86) or the mighty Honda F20. A low red line and turbocharging make it a usable daily, and remember it’s all for the fuel economy tests, when they don’t spool the turbo. In real life, they get just a little better fuel economy than a NA V8. The only improvement is because they’re a few pounds lighter but more complex. The mistake here is like you say, attempting to move a heavy family or luxury car with less than 8 cylinders is a bad idea, no matter how many turbos or automatic shifting gears you throw at it. Inline-4s are better suited to small cars, period.
Also, I see V6s having a bad rap these days, I don’t know why, because some of the best cars ever made had a V6 or VR6. Hello NSX, Alfa Busso, Golf R32, Lancia Stratos, Alpine A310, Nissan Z, Dino, ATS-V, 3000GT VR4, Nissan GT-R, Evora 400… and don’t forget the new Camaro 1LE, AMG C43 and Ford GT.
Finally I don’t think all-electric cars will take over anytime soon. If the goal is to reduce emissions, you still need hydrocarbons to generate electricity unless you plan to dot all of Europe and America with nuclear power plants. Plus, batteries are heavy, inefficient, don’t last long and when they are being made they cause way more polution than ICE cars and need exotic materials only found on certain countries like China. If the electric shift was good and inevitable, it would happen with or without a government mandate.