I am tainted by the leak, but I promise nothing here is hinted at in any shape or form in the artbook. These are mostly not new ideas, I know – but the discussion seems to wind down here anyway…
Alright:
What if we really have to destroy the blood moon because otherwise the land is just overrun again and again by stronger and stronger monsters?
They are out of ideas and just crash the whole damn thing on the planet (nod to Majora's Mask) and by that cause a huge flood.
Or we need to do some kind of cleansing ritual to wash away the malice by endless rainfall and that would raise the sea level as well (= tears of the kingdom – this would explain why they considered the title a spoiler…).
The incentive for doing sidequests would be huge in this case. You could help all people of hyrule fleeing to a safe island in the sky (maybe an expanded tarrey town). Otherwise, they would drown in the flood, if you go to the end boss right away. A bad ending that would earn its name - I would say...
Flooding Hyrule like in Wind Waker kept me further thinking and now I already want a third game in the BotW/TotK style and with this map - but even more drastically changed. I just love the artstyle and the world building and would like to have a continuation of that.
I am playing Subnautica – Below Zero right now (loved the first one) which might explain my dreams.
So Hyrule is almost completely submerged, only the mountaintops are left as islands. The sky islands descend and agglomerate to form a few regular islands with unique flora and fauna. Let another 1000 years pass. Hyrule is now covered by reefs and underwater vegetation, all the old ruins, towns and hyrule castle are completely overgrown and degrading further.
Let me explore that ocean subnautica-style with upgradeable diving gear, getting deeper and deeper until we swim through the deepest caves (that might now be in TotK), using a weird Sheikah/Zonai submarine in the endgame.
Let me fight giant enemy crabs and hellish deep sea creatures. These leviathans we only have seen the bones of in BotW swim once again through the ocean. Maybe they could perfect navigation and combat underwater like they probably do now for the air.
And on top of all that make the land mass west and north of hyrule one giant new explorable island, where horse riding is once more a good means of transportation, and there you have a more classic Zelda gameplay approach.
Should be a new Link anyway – so finally use a female Link please.
And not Ganon/Ganondorf or anything like that again. Create a new and unique threat (no ideas right now).
That's all I ask, thank you