They are tightening the screws. They have a lot of possibilities... their rook can make several good threats if they can prepare them correctly. For instance, blocking our bishop's protection of c1 with g5, followed by Ra1, then Qc1, threatening mate on our back rank. But if they make the mistake of pushing the passed pawn too early, then we still have our RxB threat. I am recommending h4. Any other thoughts?