Halo 4 plot. And halo ce...?

Ok so quick question for everyone who's played every relevant halo game (I.e. Not halo wars), what is going to be/ or possibly going to be the plot of halo 4. And also in the 10th anniversary edition of halo combat evolved, is it going to be an exact copy of the original with a face lift, or are there going to be slight changes in the actual game?