Be headed for(chess)

The latter. (but the context may suggest the former as well)

I would say it means that the **** is certain, or at least very likely, to be promoted. It would be pointless to describe its direction since pawns always move up at least one row every move.

Are you sure?Can it have any other meaning?

I can't think of anything else it would mean. Do you have the board set up for this game? Where is the **** and what else is going on? If it's on row 7 and Black has no way to stop it from getting to row 8 and being promoted it's pretty obvious what is meant. If it's on row 3, and Black declined to take it when he had the chance, it might be that the author is using his knowledge of the outcome of

Expected to be or certain to be?
Ie. did it go forward with the hope of getting a promotion, or is it certain to?

Yes, it's on row 7 and there is no way of preventing it from the promotion

White could choose not to move it up (for whatever reason), so in that sense it is not certain. However, we would normally expect to see White move it up for a promotion, and presumably the author knows how this game turned out and knows that White made the obvious move. We would probably be astonished if White did not move up the ****.