https://youtu.be/yAF9XlluONA?t=43

Given that (apart from MM, which I never could get into) BotW is my least favourite 3D Zelda, I'd be more happy to see them move along.

But then again, since BotW felt to me in the end more like a gigantic tech demo than finished game, maybe this is not a bad thing and they hopefully make a good story with plenty of proper dungeons in what is already nicely created world and that way fix at least some of many of BotW's problems.

Well, that's half the development time as Breath of the Wild right there.

Yes, because the mindset and mentality behind developing DLC expansion packs is totally the same as that of developing a brand new game. 

Even if it's the exact same map, that doesn't mean there isn't a hell of a lot they can still do with it that they haven't done by implementing different elements and ideas that lead to all kinds of possibilities. As a matter of fact, the Zelda team has already done exactly that before:

That's just the thing, if its the same map, will it even feel like a new game, or just BOTW DLC Pack 3, just at $60?

A Link Between Worlds certainly didn't feel like a $40 DLC Pack, and that game uses the exact same map, almost 1:1, note for note, as A Link to the Past. But it was still a fantastic game that did enough to stand out on its own with kinks and things like the wall-merging and item renting mechanics which opened up all kinds of new possibilities for puzzle-solving, exploration, dungeon design, speed-running, and nonlinear gameplay that weren't possible in A Link to the Past. 

They pulled it off before, they can most certainly do it again.

I didn't play ALBW. I just can't see how a game can possibly feel like a full-fledged new entry in the series with a recycled map. I can't imagine any amount of new mechanics or story not making it feel cheap and half-arsed.

Yes and no.  Lore wise it is the same, as is the case with any version of Hyrule.  Gameplay wise however it was rebuilt from the ground up.

In this case it is implied that it will be more like Link Between Worlds, where it is a 1:1 match, but altered/expanded to fit the game's theme and keep things fresh.

Just because it showed Hyrule Castle in the trailer, that guarantees nothing by itself.  It could have easily shifted to a neighboring land or a Termina type of scenario for the game itself, which seems to be what many people were thinking before this news.