By Janice Wald Henderson Wild excursions, on-board activities, and remote destinations. Just when you think you've seen it all on the rivers and high seas, a new ship or line (or a major vessel makeover) dangles an irresistible opportunity. Perhaps you dream of living like a rock star, diving deep into polar waters, discovering a new hobby, or making a wish – such as meeting Broadway stars – come true. We scanned the horizon to find out what’s next at sea. For veteran cruiser