No, No, and... NO.
First it's 900P not 720P, and it would either need to be upconveted or have letterboxing.
Second, PS3 and X360 aren't rendered at standard def when set to high def, the PS3 actually has a non-standard def for it's higher end output. The games are rendered depending on need, some support 1080i natively and even 720P natively, but it needs to be developed that way, and while the PS3 does often use the hardware upscaler to help make the task easier than full res HD, it's not limited to it.
Lastly, HDMI on the laptops is an output, not an input.
I have the exact same laptop the OP was talking about in the original post, and right now there is no laptop solution for input, although there are external solutoins that would 'kinda work' in HD with a bit of lag, it's not via direct HDMI input though.
Wait for spec ExpressCard spec 2.0 to be included in fall/winter laptops, and then I would expect an input card shortly after that (with DRM all over it of course) similar to the Black MAgic desktop HDMI solutions .