I'd guess that the next Zelda game is more likely to be a top-down style of game, as they are often released in between major 3D titles, due to them being far quicker to produce.
As for what system it will be on, I'd typically expect it to be on the 3DS, but with releases slowing down I'm expecting it's lifespan to be ending within the next couple of years, around the same time we can expect the next Zelda game... so I think some sort of sequel to the 3DS is more likely... either as a whole new system in it's own right, or as a sort of "Switch Lite" (a smaller, budget version of the console with a partially shared library)... with the next Zelda possibly being a release title for that system.
Story-wise, I do still believe the timeline to be canon, but think that BotW is located on a new branch of the timeline, and think that the majority of the references to past games within BotW are not actually referring to the events of previous games, but are actually referring to similar events that occurred within this new timeline that have yet to be depicted in a Zelda game... this gives them a huge amount of flexibility when it comes to adding in additional games into the timeline, and allows them to revisit concepts and characters from past games which would otherwise be impossible to return to without causing inconsistencies.
As for what system it will be on, I'd typically expect it to be on the 3DS, but with releases slowing down I'm expecting it's lifespan to be ending within the next couple of years, around the same time we can expect the next Zelda game... so I think some sort of sequel to the 3DS is more likely... either as a whole new system in it's own right, or as a sort of "Switch Lite" (a smaller, budget version of the console with a partially shared library)... with the next Zelda possibly being a release title for that system.
Story-wise, I do still believe the timeline to be canon, but think that BotW is located on a new branch of the timeline, and think that the majority of the references to past games within BotW are not actually referring to the events of previous games, but are actually referring to similar events that occurred within this new timeline that have yet to be depicted in a Zelda game... this gives them a huge amount of flexibility when it comes to adding in additional games into the timeline, and allows them to revisit concepts and characters from past games which would otherwise be impossible to return to without causing inconsistencies.