The effect of compiler optimizations are not trivial. Sorry, that's a fact.
Well sure. To the lazy people who write unoptimized code, compiler optimizations have a significant impact. But you can't have it both ways. The more optimized you think you're making your program, the less room there is for the compiler to fix your sloppy code. But using my example, running a Python version of Crysis would only run 1.33 times faster than a quad-core 3 GHz machine since 996 cores aren't even being used.
Yes they are. The scheduler, not the compiler, determines how many cores are being used. If you wrote your engine in Python, and Python had kernel level thread support, it would scale automatically to take advantage of improved hardware. That's the advantage of JIT compiled/interpreted languages as opposed to the pre-compiled binaries, who stop working when hardware changes. Don't believe me? Play any game from 10 years ago. It's the same technology (Windows, DirectX blah, blah, blah) it just doesn't work anymore. No try the same with something written in Java. Not only will it still work, it will work better than it did 10 years ago, because it takes advantage of the fact that technology isn't static. Optimizing something to run from 10 FPS to 20 FPS on a GeForce 2 may make that same program drop from 120 FPS to 25 FPS on a GeForce 7800.
So you agree that optimization is a waste of time then? Good. But even in this case, it's a gamble.
Every thing's a gamble. Writing your game in C++ is gambling that a year or so after your game has been released, no-one will care that it doesn't work any more. Which one of the following would you prefer:
I don't think your estimates of the time-to-market for a video game is even remotely accurate. If it took 12 months for technology to catch up, I'd spend that extra time improving on the game.