It seems possible that if the Titans return, they might feel included to start killing us all. Why?
Well first off there's the Curse of the Flesh. At the least it appears that dwarves and definitely gnomes are corruptions from the Old Gods. Reversing the curse could be fatal. Or we'd fight against it, triggering a war. However I must admit to not fully understanding this. It appears that Loken and his minions are waging a war against the squishies (us) and are trying to convert the gnomes back into mechanical beings. However he's been corrupted by an Old God, and it's the Old Gods which created the curse in the first place. Maybe I misread the lore or I'm making a false assumption somewhere.
Humans may also be a part of this corruption. From quests that I've not done, but heard about, it seems that they may be deformed Vrykul. Again, this is a problem possibly caused by the old god whose name I can't spell but whose blood I make into arrows.
Elves? Trolls? They seem linked to each other, with trolls being first. So what are the origins of the trolls? Based on their extremely savage nature and tendency to summon big and evil things (Hakkar) or just do generally destructive things (killing their own gods), they may be in some way linked to the Old Gods.
The presence of Draenei and Orcs might not sit so well. Let's be honest: they're aliens.
Moving on, let's try to step back from our perspectives. The dragonflights are here to protect Azeroth, to maintain it. We have repeatedly gotten into fights with them. The black dragons are the obvious one. Despite their leader being insane and evil due to corruption by the Old Gods, the Titans might not see things so much in our favor. Then there are stories of heard of killing Malygos, the leader of the Blue flight. That's a big no no. Throw into the mix the many lesser minions of the dragonflights we've killed. Oh, and I have an important green dragon's essence in my bank.
On the other hand though, maybe the Titans will see our value. Despite the corruption, we are the ones fighting back the Old Gods. We are maintaining balance far better than might be expected. Sure we brought the Legion, but we also beat them off. Repeatedly. We're hardly perfect, but for a lot of untrained, cursed beings, we've done a decent job. Compare proto-drakes and dragons. Could that be the next step for the sentient races? I wonder if the mages of Dalaran would replace the Blue flight. Perhaps shamans could take over for the negligent Black flight.
I suppose we'll see as more content comes. Or it never happens and two years from now we invade upside-down Azeroth and we're all back in Karazhan.