i think its in the failure time line, takes place in between Ocarina Of Time and A Link To The Past, and if this is the case i wouldn't be surprise if this Link is a resurrected one from Ocarina.

the world is in ruins, so after zelda 2 or after wind waker

Tangent - Is 'A Link Between Worlds' just flat out an alternate universe of the Failure timeline?

Otherwise I don't really see how or where it would fit in.

There is a theory that supports that Dragon Roost Island from Wind Waker, is in fact Death Mountain.

The dungeon there is fire based and full of magma, there is a volcano called Fire Mountain just south of it and it also has Bomb flowers, just like in Death Mountain.

I like your theory, but the lack of water does raise a big question.

Also, Ganon was never referred by that name in this timeline i believe, he is known by his humam name/form, Ganondorf.
Finally, the image we believe to be from Hyrule Castle would be missing the Tower of the Gods.

Dragon Roost has a higher chance of being Death Mountain, but Fire Mountain is way too small, just a mini dungeon in the game

NintendoLife is also posing this question and they do bring up some good points

http://www.nintendolife.com/news/2016/06/talking_point_where_does_the_legend_of_zelda_breath_of_the_wild_fit_into_the_zelda_timeline

Looks like there were crossed wires somewhere along the way. From what I can see, it wasn't that it was a "rumour", but a "misunderstanding".

Did you play through Skyward Sword?

Because Calamity Ganon sounds suspiciously like Demise, and Ganon is supposed to be the result of Demise's curse, so Ganon's soul essentially becoming Demise would be a natural progression... but the people of Hyrule wouldn't know who Demise is, so it would make sense for them to refer to this thing by the only name they know it by, which is Ganondorf (but of course, it always becomes "Ganon" when no longer in a human-like form).

The lack of water makes perfect sense - the sea has drained. This is Hyrule after it has been flooded, and then the waters have receded. As I pointed out, Link can find "Rock Salt" from an "ancient sea" on a plateau. There's only two ways that can make sense - either there's been major changes in geography due to severe tectonic activity, or the plateau was once underwater.

And the Tower of the Gods was raised from below the water in some way, and it's unlikely that it was on top of Hyrule Castle beforehand, since it is described as "a place that the gods of the ancient world prepared so that they might test the courage of men". It's not going to naturally rest on Hyrule Castle. People have observed that the Tower of the Gods sounds suspiciously like one of the Shrines in BotW.

Incidentally, here's what the boss of Tower of the Gods looks like:

Notice something? Look at the fingers. Now think about the colour of the magical stuff in BotW. Now think about the overall design, and compare with the Guardians in BotW.

There's more to consider. The region we've been able to play in contains a plateau, a snowy mountain and a forest area. Do you know what's right next to Forest Haven in Wind Waker? Ice Ring Isle. And on the other side of Forest Haven? Cliff Plateau Isles.

That is an interesting take on it. So essentially Ganon is reverting back to Demise in  his pure form. Hm...

The sea "washed away" Hyrule though, at the end of the Wind Waker. That was the King's wish to the Triforce, to start anew. I agree the Koroks showing up has got to mean something.

The game has clues from all timelines. Geography and features from the OoT-TP line, characters, esthetics and audio cues from the WW-line, and the ruined, 'evil won' theme from the ALttP-AoL line.

I haven't read enough about things to make up my opinion on this yet.

It will be at the end, and will unite the three timelines in a single one.