Getting bought is not an option as neither IBM nor HP would tolerate this - relabeled Brocade hardware is central to both companies.
Buying Mellanox -albeit cool- would just give them another niche unless the could add mellanox IB technology to their etherstuff. otoh, the ethernet market is corned by cisco, so it would not make sense.
They might concentrate on "anything but ethernet" with mellanox, but.. dunno, is this worth it? Mellanox would not come cheap.