I think the saving grace here is that Darkspear are already jungle trolls. They are going to feel right at home with the Zandalari aesthetic, much more than forest or sand trolls would have.
And we might see some developments linking the two more tightly together. From the little we've seen, Rastakhan seems to have a daughter who will be prominently featured in the quest zones. It may sound like a stretch, but I wouldn't be surprised if this daughter ended up taking over and starting some sort of relationship with a resurrected Vol'jin.
They would make a good goblin Allied Race imo. They don't have the same model, but both races share a connection through their mutual past enslavement by Deathwing and both have a few shared features.
The Horde should really get the Stonedark drogbar and the Alliance should really get the Tideskorn vrykul.
No they were called 'stone' trolls at one point in development, they've gone through a lot of different iterations, one concept art had them as bears with moose horns, and xal'atash calls them a failed titan creation implying they're some kind of ubertrogs, so they're a mix of a lot of things.
Twas brillig
Well it's not really 'canon' but the similarity is there.
There's a bit of debate on whether the Zandalari bits are stone (I think they are) or whether they're reptilian scales (from interacting with dinosaurs so much), and whether they're naturally grown from Trolls being 'evolved' elementals, or whether they're something the trolls jab into their skin and then 'regenerate' over to grow natural armor.
Twas brillig
idk, i feel the look of the darkspear is pretty distinct from the zandalari. they're much more tribal looking, with voodoo-y aesthetics. while the zandalari are mayan/aztec and look more... civilized.
i would love to see all the orcs, trolls, and tauren eventually under the horde banner. the alliance has numbers on the horde right now. only the forsaken is comparable in numbers to any alliance race. so it'd be nice to see the horde bring in more people.
I have to admit, the fact that highmountain tauren can have massive moose antlers looks highly badass and might just push a lot of the tauren off the map.
Don't worry though, because anything highmountain can do, tauren can do, and tauren can do things highmountain can't. So you'll still see plenty of paladins, priests, death knights, etc.