I love how half of the people are like "This looks just like any other Zelda game, why don't they do something original?" and the other half is like "what's wrong with the original formula, why did they have to add something as stupid as a train?"
1st of all, if you don't like the Zelda formula, shut up and go play a different game. Obviously they're not going to make a Zelda game for the people who dislike the series anyway. IMO it's still the greatest games series out there, you don't have to change a formula when it works, and it does.
2nd of all, stop booing away every little bit of change, people. from what I've seen, the train's probably faster than the boat, which is a plus. You probably also won't have to draw out a map, you'll just have to pick which track you want to go on when you read a split, which will also make it faster.
3th of all, this is the next 2D-style Zelda game, and I honestly prefer the 2D games over the 3D ones (but not by much). If you want a 3D Zelda game, wait for the next Wii game, but don't expect them to not make any 2D Zelda games any more, seriously.
Even if this game is only PH 2.0, I wouldn't care. The dungeons in PH were quite original (spare the countless revisits of the temple of the Ocean King...), and I wouldn't mind seeing more.
About where this all fits into the Zelda time-line... don't bother. There isn't even an official time-line theory, there's a lot of different version. We know how some games belong together and which game comes 1st (most of the time), but there's no definite answer to how the games follow each-other.
The fact that Zelda is in the game and the lack of water suggests that this is not the Wind Waker universe (which is also the PH universe, BTW). So, the possibilities:
1) This game either comes before Wind Water, before the flooding of Hyrule. (Which means we might get some more information on this)
2) This game comes after WW, but everything dried up (this is also part of one of the time-line theories anyway)
3) This game does not take place in Hyrule, but somewhere else (which has been done before, just think of the oracle series and such). In that case, it can be anywhere on the time-line
4) This game is part of the Adult link time-line (which probably puts it behind TP)
5) This game is a direct sequel to PH, and Tetra suddenly decided to put on a dress...
6) It's all a dream... Again
As we don't know ANYTHING about the story at this point, there's absolutely no point in speculating. So as I said before, don't bother. I don't know much about the time-line theories and how they were established anyway, so there might be more possibilities than I listed, and some might as well be impossible.