Now that we have rivers, Notch could add different sizes of boats (galleons, sail boats, et cetera), and have pirates or marauders that travel around following rivers and coastlines. They would have an advanced AI so that if they saw your house from the ship, they would anchor, send out a dingy and raid you! Sounds complicated, but I think it would be a decent addition to go along with NPC's and villages.
**** YES! Every update recently (For the most part) has added something I've wanted for a long time. 1.5 brought rain, 1.6 brought [official] tall grass, 1.7 added a legit way to get leaves (Screw pistons. :p), etc.
This update is bringing a TON of things I've wanted...Improved biomes, rivers, better farming options, and a ton more.