I "finished" Breath of the Wild a few months ago. Found all the shrines. I absolutely did not find all of the Korok seeds, I didn't even find a third of them. They're fun to find by accident, but hunting them all down would be madness.

And we've just learned from E3 that the sequel is "in development," as if that could be doubted. Maybe it was the specific language about it being a sequel to Breath of the Wild, and not just a new installment in the series. Maybe they've said the same in the past. I've done no research.

It was such an amazing game, I'll go back to it for ages. 

One trades in a Korok seed to a...big, uh, Korok seed guy. And he gives you more inventory space.

Consider this option: if you can acquire for cheap a Wii U, Breath of the Wild is fine on that console. That was how I played it. Bought a used Wii U for $170, no regrets. Now that I have the Switch version of the game, I actually have a very uncommon opinion that the Wii U version is better. It probably runs 10% worse (who cares right?) but the key difference is that (just my opinion coming here) the Wii U pro controller is better than the Switch pro controller. The Wii U one's analog stick placement makes doing "the claw" (look it up if you don't know what that means) easy. Doing the claw on the Switch controller is way harder. And BotW is a good claw game.