Asking the question about the trapped elves has proven to be interesting. We really have no idea if it's true at this point, so it's just idle speculation and what-if. But I have found that when asked, many people will introduce reasons why it's okay to let the trapped elves die in order to save their own people. Which I get. It's fair. Anyone would want to save their people and look in horror on others who would have them die for any reason. But "they're old and probably tired of life" is just another way of saying something like "it's a world full of tranquil" to me.
'Sides, when did we get to where it's okay to kill old people for being old and wanting a nap? 
And that is why I get confused on how people don't understand Solas's reasons for thinking the way he is. It's not a good thing, and causing the death of a lot of people is terrible. But when given the exact same situation where it's completely equal -- if the elves die, Thedas lives, but if Thedas dies, the elves live -- people are going to defend saving Thedas. Even if you don't agree with what Solas intends to do, and I don't, not at all understanding where he is coming from when you'd do the same thing in his situation is kind of baffling.
Naturally, this doesn't mean anyone has to like him or agree with his plan or not want to kill him. That's all valid and fair. And again, I don't agree with his plan either. I just like having an antagonist I can understand, and to where I can look at their reasoning and make sense of it. It's nice getting to see the other side of an antagonist instead of just facing down another black-and-white villain, you know?
People justify Solas action by imagining there's some elves trapped somewhere.
And no I can't for the life of me understand Solas reasoning.
The ancient elves who survived are still alive , like him , the Sentinels and Felassan.
The current elves are the children of ancient elves...while he was sleeping , his people kept on living and had children.
So who is he saving exactly?
The ancient elves still alive and who don't need saving?
The current elves he's willing to sacrifice?
It's not if the elves dies , Thedas lives etc...
The elves are alive right now , it's not about elves ...it's about sacrificing everyone so immortal , magical elves will be born again.
Immortal , magical elves had their time under the sun , they destroyed themselves , no one else did , they were so powerful , they were about to destroy the world , Solas had to sacrifice the part of the nature of the world , and the nature of his people to contain the threat.
And now he's the ancient immortal magical elf who is bend on destroying the current world.
Maybe immortal magical elves are the one broken , no?