This bring me several questions to my mind. So how did psx became a success if you say that core has a low margin? What is low margin for you?
It wasn't low margin then; it is now. Generally as markets mature the chances for profits decrease over time.
The early days of a market segment or industry are very risky but also very profitable for those who win. Consider the early days of "core" gaming; companies and consoles like Atari, Sega, TurboGrafx, Commodore 64, Nintendo, and Colecovision.
In the early days of gaming, there was enormous turnover and lots of failure. Most of those companies and consoles no longer exist or are shells of their former selves; in fact, only Nintendo is still around in the same capacity they once were. But it was also a time of enormous year-over-year growth and profit, allowing small companies to get much, much bigger if they played their hands right.
Compare that to today; we've had the same 3 companies (Nintendo, Sony, Microsoft) as the only real players for 15 years straight now. The market is much more stable, and safe, stable markets don't tend to be highly profitable.
How do you claim that it's impossible to capture core and casuals in the same machine when you can see that's what happened in Ps2, NDS and X360?
I do not at all agree that 360 captured a significant portion of casuals, but in general, the answer again is that the market has changed. Things change. The competition has gotten better.
Apart for that, in my opinion this kind of analysis are always shortsighted, it happens the same in every industry and you can see it clearly in the stocks market. The flavor of the week changes every week indeed, so you better make a business plan with a few years of foresight it you want to keep afloat. This strategy have proved itself to work, what happened with Wii as Wii U shows for now it's the exception that confirms the rule. (I don't know if you have this idiom in English).
Right, it's always a trade off. Safe, secure, reliable markets like "core" gaming are also typically the ones with low profit margins; risky, burgeoning markets like "casual" gaming are the high profit ones.
You cannot realistically expect to have both a safe, reliable market and a market with high profit margins for long. If "hardcore" gaming were both safe/reliable and profitable, then lost of other companies would be jumping to make new consoles and compete with Microsoft and Sony because every company loves the sound of markets like that.
The fact that nobody has shown any interest in entering this market for nearly 15 years tells us quite a bit.