Paul I look for more security before the cruise such as a cannot cruise list, like the airlines have a no fly list. Body scanners are probably in the works too.
Onboard ship I think we will see armed security guards instituted, especially in areas where pirates are known to frequent the waters. The institution of "Catch nets" installed around the sides of the ship to catch those who would commit suicide.
These are just a couple of ideas but rest assured that our over regulating government will come up with something.