no, it simply has a lot of PS3 based jokes in it and is designed for the system, while also being a pretty big title.
so porting wouldn't be easy, and they would not only need to port, but also remove or replace a lot of jokes and easterggs.
like you can change the controller port during the Mantis fight, and if you do that there's a whole codec call where they tell you that this isn't MGS1, and that this doesn't work here.
or as you go down the stairs in Shadow Moses, where on PS1 there was a disc change, Otacon will call you and tell you to switch discs, until he remembers that you're playing on a PS3 which uses Blu-ray technology
there are other smaller and bigger things with PlayStation eastereggs and PS3 specific jokes and homages.
the controls would also need slight adjustments, like shaking the Dualshock 3 would change your camo quickly.
then the dialog would need to be rerecorded for button promts, because characters will literally tell you to press certain Dualshock 3 buttons if I remember correctly.
so in short, the issue with MGS4 is 1: it's a game designed for the exotic CPU of the PS3 and 2: it is full of PS3 system specific jokes, eastereggs and spoken dialog