I think it is the easiest way for Merck to buy Vertex to gain competition edge on HCV, although it is less likely. Rumor says if VRTX pps stays in the 30s, it is a hot target for potential buy who is willing to pay only $60 per share.
J&J buying Vertex sometime in the next year seems to me like a better possibility. They are already partners on Incivek in europe. Still, I believe it is unlikely Vertex will be acquired, mainly because they do not seem to want to sell the company.