I think it's very unlikely that they'll do it. For one, there would be no cameo and any mention would have to involve why god!Inquisitor wasn't helping the heroes. Unless both of the next planned games involve smaller scale stories like Hawke's, they would have really no excuse for not bringing the god!Inquisitor back. Except, you know, gods make conflict difficult.
I'm actually not certain we'll see Solas again until the end of the series. If what he does is seriously world changing, they may not want to deal with the aftermath of the changes. I agree that they aren't going to kill him off in DLC though. We're probably not going to really see him again in DLC though. There will probably be some mention of what he's doing though.
If he's an antagonist for even one game, he and Lavellan aren't going to be together. If he dies at the end of that game, he and Lavellan aren't going to be together. Like I said, taking away his power is one of the very few ways that he won't have to die, disappear, or be an enemy. It's better than a lot of endings he could have.
He may not show up again post-ending of DA:I, depending if they want to do a "bridge" DLC between DAI and the next game.
As for the Inquisitor being god-tier... would not be the first time that your previous PC mysteriously disappeared or was too busy with something else to come and help you out.
You are very Team Pessimism today, aren't you? I don't think Solas has to lose his power to disappear, and I think he's more morally ambiguous than a straight-up villain.
As for not thinking Lavellan could be with a villain, well... Anders isn't Mr. Sunshine and Rainbows, but it seemed to me that he was going to come crawling back to Hawke if allowed to live. I'd consider Anders more than a little bit villainous--sure I know he tried peaceful methods, but in the end his actions hurt more innocents, not the people who had caused the harm he wanted to change. And yet... Hawke and Anders can be together.
If there is a DLC, we may see an Anders-style choice where we get to decide whether or not Solas lives. But again, it is more likely we'll see a bridging-the-gap type DLC, will be able to choose whether or not our Inquisitor wants to join him/stay with him at the point she finds out what he's up to, and then he'll show up next game and maybe offer advice or help with the fallout of whatever happens because of what he did. Which, as another pointed out, is probably not going to be entirely negative.
If we're right about what he's up to (dropping the Veil at least, not necessarily freeing the gods, though that may be a side effect,) POSITIVE benefits include:
- Elves regain immortality, immunity to disease
- Everyone has magic
- Harder to corrupt spirits into demons
- Spirits and living creatures can begin to understand each other better
Now we've already gone through all the negative stuff that can happen, pretty much, but... those effects? And knowing Solas wants to help people?
Though I kind of wonder if one of the reasons he left was because he believes he'll have to set himself up as god-king of Thedas, and that's not something he wishes on Lavellan, nor is something he would be able to trust her to share (because past betrayal). And that... might put him at odds with Lavellan, even if he weren't a tyrant.