To a lot of people this is pretty well-known already, but this seems to be the pattern that Nintendo likes to follow in their 3D/console Zelda installments. So let's break it down: All the 3D-styled versions of Demise/Ganondorf/Ganon fought thus far from the N64, Gamecube, Wii and Wii U titles.
OoT: Ganondorf, Ganon
MM: N/A
WW: Puppet Ganon (controlled by Ganondorf), Ganondorf
TP: Ganon, Ganondorf
SS: Demise
Alright, from this the biggest thing of note is that in the 3D titles, we seem to ALWAYS fight Ganondorf, the Gerudo King in some shape or form. I'm not going to say this is set in stone or a guarantee that Breath of the Wild will have a Gerudo version of him, but hey who knows this could very be the game that breaks the mold and we're in for a helluva surprise. This is just personal hopes here, but I hope we fight a Gerudo version of him again. I've always enjoyed and highly anticipated the final climactic sword clash between Ganondorf/Demise vs. Link.
LionHardt made a great point above, Demise being able to take on larger forms (ie. the Imprisoned) seems to be a skill/characteristic that he's able to also use, because Calamity Ganon is a huge swirling dark cloud that seems to also have the boar demon form we've seen him take on in a vast majority of the 2D/top-down/handheld titles we've fought him in. And if you'll notice too, there never seems to be a Ganondorf/Gerudo King to fight in those titles, we usually face off against Ganon, and as far as I can remember we've never had to fight a Ganondorf. He got honorable mention in LttP's back story and Four Sword Adventures, but other than that, Ganondorf is pretty much forgotten there.
We haven't seen a 3D title yet where the only form of Ganon that we go up against is just the boar demon. The level of threat and damage this incarnation of him has caused seems to be the worst we've seen him do yet, and it took having him sealed up in Hyrule Castle and not the Sacred Realm or Twilight Realm (and I guess when he got stuck in Lorule with Yuga) to contain him... so where's the Sages in all this? How bad have things gotten and exactly how crazy powerful is Ganon now that the only hope for Hyrule is a resurrected Link that either already fell at Ganon's hands, or some other Link from an age long forgotten? I can't wait to find out
TL;DR version: Ganon's a BEAST. We're in for a treat