More specifically, an ARPG. There has always been debate over whether the Zelda games are RPGs or not. Personally, I've never thought of them as RPGs, but this one in specific contains a lot more in terms of RPG-esque aspects (something I had really hoped for), so there can definitely be a case made for it as being an RPG. I'm still not sure, though, because even though it gains a few RPG elements, it fails to retain others from previous games. It also still plays more like an action game than anything.

Have you ever thought of the series as RPG? Do you think that the new one can be considered one?

Depends on how you define RPG. I define a role-playing game as a game that allows you to adjust and customize a character (or characters) to accomplish specific roles - to "role play." According to that definition, no the The Legend of Zelda: Breath of the Wild is not a role-playing game. But also according to that definition, many JRPGs aren't role-playing games either. 

I consider the Legend of Zelda series to be an action-adventure series. 

The only Zelda game that somewhat qualifies is Zelda II. The rest are most certainly action-adventure games.

Breath of the Wild looks to continue that tradition.

I mean, you do customize and adjust your character in the new Zelda. You change any part of your outfit in order to survive conditions in different climates. And all of your weapons have different, more defined numerical attack powers and traits. Can you be more specific about what you mean?

Action Adventure RPG? That's the best way to describe it.

stats on armour and weapons, crafting system, cooking system, you choose how you wanna play the game and where you wanna go, enemies have levels, open world, puzzles, dungeons. yeah, it's an action rpg. Before I would say action adventure with some rpg elements, but this one is an action adventure rpg.

You can't change the role really. Link is link. 

so the witcher and mass effect are not rpg games????

I've always viewed Zelda as an RPG game.

Zelda was never an RPG previously except for maybe Zelda II, as was mentioned previously. Up to now, the series has basically been pure action adventure. It sounds like Breath of the Wild may have some RPG elements, but at the same time, just having some RPG elements doesn't necessarily make something an RPG.

It depends on the final product, really. Breath of Wild may fit RPG at least as a sub-genre, but it will still be action adventure first and foremost.