I agree Nicknero. Valve has gotten reviews here and there from their games and it's the same thing on the graphics "It's still Valve's source engine... But it looks good for it's time."
If i were a game developer, i would not settle to keep this source engine for anything else. It's a VERY well made engine, don't get me wrong. But something outdated and something so great can be made into a better version, and you are asking for not only big sales in the market, but also good reviews, a good game that belongs to a good series, and another success.