[DGthe3]

We're already beginning to see a decline in hp in the midsize segment as V6's are replaced by economy tuned turbocharged 4 bangers. That said ... 250-300 hp in those cars is a bit much, and a loss of 50 hp isn't going to be too much of a problem for most of those buyers.

That said, it won't be like the 70's, for a number of reasons. Back then, manufactures switched from SAE gross hp to SAE net hp. This meant that engines had to be tested as they were in the car (ie, with the emissions equipment, belt driven accessories, air filter, and everything else). That probably dropped hp ratings be 15-20% on most engines by itself. The actual output didn't change, they just began measuring it in a more honest manner. On top of that, you had emissions standards for the first time and they were pretty ambitious so manufacturers were forced to detune their engines substantially in order to be compliant.

Now, things are being driven by fuel economy. Sure, the manufacturers will probably revise the fuel map, go with less aggressive cam profiles, and go down a bit in displacement. But at the same time most cars will get lighter which will at least partially offset the drop in hp. Plus, technologies like direct injection & variable valve timing will become ever more common and improve both performance and fuel economy.