Personally, I would have rather wanted to see a revamped version of dungeoneering.
that's basically what sailing is
The main issue I see is that the game is already highly sectioned up by water. It's used as a barrier for places you can only reach by having certain quests and such. If they're going through with this they either will have to be REALLY creative with preventing people from going to those places, or it's going to be some lame invisible barrier or something. Just sounds really wishy-washy in that aspect.
sailing to different areas probably requires higher levels, the excuse they'll likely use is "high currents in this area which your boat cannot handle!"
there has been a image file leaked somehow from last year

also 17m cash stack from agility right now
edit: this also popped up on a dev's twitter 4 days ago
