Well I find it interesting that Price is the only character to appear in all the games, even thou he died on a secret mission in WW2 to disable the sister ship to the Bismark and then appeared in the sequel as the same freaking guy.

quote

Counting bodies like sheep to the rhythm of the war drums

I'm rather certain that none of the SAS are Cpt Price, Soap, or McMillan. I think it's just going to be a mini plot that will be slowly revealed in IW's next game.

Price IS in the last level. He's in the pick of the 4 of them at the end of that mission and how many of you are in the plane in that mission . . . 4, he's clearly heard at the begining of it saying "WE'RE going deep, and WE'RE going hard". Hell knows about Soap. You never hear him speak anyway
It doesn't really have to tie in.
The only thing is that through out the majority of the game your the S.A.S and that's the sort of thing the S.A.S typically do.
The S.A.S don't usually fight in wars, they're specialist