Let me start out by saying that Nintendo has said there will not be a 3rd batch of dlc. But I don't think that will be the case because Botw is still under a year old and so incredibly popular and Nintendo likes to spring things on people. So I made this theory anyways even though it goes against things directly stated by Nintendo. Mostly because I want a better ending and I'm super ocd about needing 2 more containers to fully max out hearts and stamina.
When Ganon is defeated it is for the final time it is important to remember that this doesn't destroy the Triforce of Power which he contained and that means it will go to the person that most closely embodies power. At the end of the game Zelda and Link set off to investigate why Divine Beast Vah Ruta has stopped working, hinting at future problems of some manner.
So what Nintendo could do for batch 3 of their dlc would be to have a situation where the divine beasts are shutting down and the Triforce of Power needs to be found so they can make a wish on the completed Triforce. A wish to revive the fallen champions as they are the only ones capable of using the divine beasts and defending Hyrule. This could include a trial to awaken each of the 3 parts of the Triforce composed of multiple challenges, just like with the Champion's Ballad, before a mega trial to prove themselves worthy of wielding the completed Triforce.
Each Triforce has a theme: Power, Wisdom, and Courage so it would be interesting to see the trials to unlock them following in that theme.
As for who would get the Triforce of Power while it could easily end up in the hands of a villain (and there are more than a few from the series that could be used like Vaati for example, or someone entirely new) I prefer the idea that the Triforce of Power would split itself between a new generation of Champions: Yunobo, Sidon, Riju, and Teba. (The Triforce has split itself before so this has a precedent).
I think that could be a really compelling and interesting story, but mostly I just want to revive Mipha and have a completed heart and stamina count. Also ffs give us a key item that lets us climb in the rain.