It's not the first time that Zelda's Hyrule Castle has made it to the final stage of LEGO's fan-created and crowdsourced IDEAS platform, and it certainly won't be the last — anything to do with Nintendo usually gets summarily dismissed, after all.
But this latest Hyrule Castle design, based on Breath of the Wild, includes Calamity Ganon, Koroks, Bokoblins, Guardians, the Hylian Shield and Link's sailcloth glider, so surely all those details will convince LEGO and/or Nintendo to put it into production this time?
BrickGallery, the designer, is also responsible for one of the previous successful (but rejected) Hyrule Castle sets, and quite a few popular Tom and Jerry sets.
As for what the "final stage" means for this LEGO set, here's what LEGO IDEAS says:
"A "LEGO Review Board" composed of designers, product managers, and other key team members will examine the idea. We'll build concept models and determine if the concept meets our high standards for what it takes to be a LEGO product. This includes factors such as playability, safety, and fit with the LEGO brand. Every potential LEGO product goes through a process like this and must meet the same standards."
This process can take several months, and at the end of it, it'll either get green-lit and go into the next stage (design and development) or it will get rejected.