I think it's a bad scenario to be honest. It would cost too much money and by time it came out, it wouldn't make them enough...not to mention, if it had 50% of the power of the true next gen consoles, it couldn't handle the games like you're saying. It would only be able to handle the shitty games, like madden or any other sports game, or any low-budget games.
I've always thought that for things like ram and HDD, they should allow you to upgrade...and right now, you can upgrade HDD. Why shouldn't I be able to buy another stick of RAM for my PS3? It would help the console perform better, and games would not be built to the upgraded specifications, so it wouldn't be necessary - if I wanted it, it would be on me..no perks aside from performance - and I'd still buy it.
That's just me tho.