I'm getting more and more hyped about ArcheAge. It's currently running on CryEngine 3 so it's going to have great graphics and physics.
They call this game a sort of a new Ultima Online. It's a PvP/PvE MMORPG with what it seems a basic hotbar combat system, but with a few nice sandbox features (no definite classes, house/castle building, factions, zone control, farming, tree planting/chopping, ...).
Features    Huge world map
    Dynamic environment
    Mass PvP (100+ people)
    Player housing
    Crafting & production
    Adjustable interface
    Mounts (e.g. horses)
    Naval warfare
    Persistent World
Thread with basic info about the game: 
http://archeagesource.com/topic/26-all-that-we-know-about-archeage/Info on factions, castle building and naval warfare: 
http://archeage-online.com/post/1718109253Footage from closed beta tests:sanbox, world development, general ingame footage - 
http://www.youtube.com/watch?v=210MpzwbhGw&fmt=18 *very cool 

massive siege - 
http://www.youtube.com/watch?v=ahz76RM_V9g&fmt=18ships, gliders, harpoons, physics, creativity - 
http://www.youtube.com/watch?v=kVWaEDqY4uQ&feature=relatedbuilding a house - 
http://www.youtube.com/watch?v=uEZPMb2bgH4&feature=relatedrandom footage, apparently mobile fertilizers? 

 - 
http://www.youtube.com/watch?feature=player_embedded&v=jSKn5LOFA1EA set of videos of YOGScast testing out Archeage in Korean beta (english commentary), first part:http://www.youtube.com/watch?v=Vo05ANVoGvg&feature=relmfu (check the links in the right menu for next parts)
They do some house/boat building too, so it's quite interesting.
They also mention in one of the vids that if you murder/pk someone on zones where pk-ing is generally not allowed you can be taken to court (you get a cutscene) and get sentenced to jail and put into prison for half an hour. You can ofcourse escape from the prison by digging your way out with a spoon or bribing the guards, lol 

Sailing through the sea sounds interesting too, you build your own boats, you can be a pirate, you encounter dangerous whirlpools, sharks or even a kraken.
Last one of the YOGScast shows footage of building a big ship and then some naval warfare 

 : 
http://www.youtube.com/watch?v=HekMwOwPzfQ&list=PLF193916B5B916DBE&index=7&feature=plpp_videoIt's interesting that Koreans actually developed the kind of an Ultima Online successor in 3D, I expected a western company to do this first since Koreans seem to be pleased with their boring grindy MMOs.