Sad and harsh as it may sound, cruise lines are just the same as any other shipping company. They are there to be successful and make a nice profit for their shareholders or principals. it would make no sense economically for them to be involved with ship preservation. The only hope is for some vessels to be purchased by non-maritime interests and converted to floating hotels, exhibition centres and the like (ala Queen Mary at LA) However, the cost and red tape involved is very often prohibitive, which is why many of these projects fail.
Phil