Throwing in my (disorganized) speculations:
First, I feel that the next major event is going to be touched off by whatever disastrous thing Solas has committed to doing, which has been suggested to be collapsing the Veil. This would not only fill the world with spirits and demons, but would make the elven people whole again, giving them back their magic and immortality. This has a lot of implications, particularly for economies that take advantage of them as a weak servant class like Orlais and Tevinter.
Solas may also be about to release his old 'friends' upon the world. I have a hard time believing he'd free Andruil, Dirthamen, Falon'Din, and Ghilan'nain, since they're the ones I believe that it's heavily implied betrayed and killed Mythal (though Mythal can't get her reckoning if her enemies aren't there to be reckoned with, yeah, she'll be back, they'll all be back). Which leaves the gods June, Sylaise, Elgar'nan, and the Forgotten Ones Geldauran, Anaris and Daern'thal as the named elves available that are also locked up. They're probably all going to want to kill him, too.
If the elves are restored to what they were, suddenly, there are a whole lot of elves hooked up to the Fade directly who aren't particularly happy living in slavery in Tevinter or scraping at the feet of nobles in Orlais. I can only see them rebelling en masse, the chaos during which would be a lovely time for the Qunari to strike. I also have a theory that the vallaslin is something like a geas and if an elf has a particular god's vallaslin that god can call upon them for service or draw power from them. So, that would be an instant, if small army of the Dalish and whatever ancient slaves like Abelas are still sleeping for the elven gods to take advantage of should they be freed. Also, I think Arlathan is going to rise from the ground, either raised by one of the gods or Forgotten Ones. It's going to be full of the nastiest Blightiest elfy stuff.
Since Solas loathes the Qun so much, and the gods are probably using slaves to fight their wars, if he's still alive, I can't see him sitting back and watching while his newly empowered, freed people get steamrollered (but he's probably going to die before he gets to cause more trouble). If he survives long enough to do it, he'll either try and beg the Inquisitor to bolster the Tevene army probably via an Exalted March (which would probably happen anyway, I really hope there's something for me to do with that 350 power I've managed to accumulate in one of my save games), or attempt to put together an elven resistance himself.
Meanwhile, there's also the matter of the Grey Wardens, who seem to be dealing with some sort of internal issue. Has another magister popped up and tried to destroy/control them? Are they going after an Archdemon before it can be corrupted? Maybe a cure has been found, but they are split on whether or not to use it. Whatever happens, griffons, darkspawn and the Deep Roads are probably going to be involved.
This is looking more and more like a very messy four or even five front war in northern Thedas, depending on how the factions(Tevinter, the Qun, the Elves, the Inquisition, the Blighted) fall out, all the while normal people are trying to cope with spirits pouring out of everything like freaking Princess Mononoke.
Thanks a lot, whoever woke up Fen'Harel.
TL;DR Predictions
1. Solas collapses the Veil, restores elven magic, looses spirits and demons to run rampant on the world
2. Elven Gods/Forgotten Ones are freed one way or another, maybe by Solas, begin to wreak their own havoc
3. Empowered elves rebel in Tevinter, collapsing their economy and infrastructure
4. The Qunari invade a weak Tevinter expecting one fight and instead end up fighting the elves, their gods, their magic and spirits
5. Something happens with all the people and creatures that are Blighted - Grey Wardens/Darkspawn/Magisters/Red Lyrium/possibly the Forgotten Ones or the Old Gods controlling them, a double Blight has been speculated
6. Something something something the dwarves in Kal'Sharok, the Carta dwarves and the Titans.
7. Possible Exalted March led by the Inquisition and their allies against the elven gods and the Qunari
8. Dragons?