I'm not sure I'd zero in on BioWare's choice of words there. I don't see much reason to view it as prophetic in any way, since... well, why? To my knowledge, it's not something BioWare's done before, and I don't see much reason to assume it here. Besides, the issue with it is twofold, depending on how they handle the Inquisitor - if they intend to completely take the character out of our hands, and "at all costs" means they have to do something ruthless stuff, there are people who are going to pissed for the same reasons people were pissed that their Hawke hated blood magic. It's an assumption on BioWare's part that really doesn't gel with how a lot of people played their character, and they're going to be angry. However, if they leave the Inquisitor in our hands, then another issue arises - if that "at all costs" is a hint, then so, I assume, is the "if possible." And to me, that sounds like "it's not possible, but hey, you can try." In the same way that the Kill Solas option sounds ruthless, the Redeem Solas option sounds non-committal and blase - "Yeah, I guess I'll try, but if it gets too inconvenient then dude's gotta go."
Bioware seems to be one of those dev studios that likes to experiment (they experimented with DAII, for example - that didn't work as planned, but I don't think they regret that they've tried) so I see no reason to assume something new is on the way. That, plus no DA game before had a proper epilogue before that had clearly hinted at the involvement of past protagonist in a future game.
So again, no reason to not assume that they're doing something we haven't seen before, be it multiple protagonist, or clever influence of new protagonist on past protagonists' choices.
Also - why assume that "if possible" is non-committal and blase" the "I guess I'll try" route? I think many people here have expressed interest in trying to save Solas, but a lot added that if it's going to be too much of a cost, or Solas steps beyond the line of redeemability, then he'd likely have to be eliminated. It's not a "blase" route, but more like "I will not cross a certain line", like I've mentioned before.
That being said... I don't think (Or rather, I hope) BioWare doesn't end up making either route to be the "right" option. Not only because, well, that means it's a fifty-fifty chance that our route will end up being the wrong one, but also because... I mean, everyone's choices should be respected and validated - imagine if the tables were turned. The option to redeem Solas is there, but it's so much worse than the one where you just kill him and be done with it.
They are respected and validated - in a sense that they have consequences. But not all of those consequences are positive - just look at people who sacrificed the Chargers for the sake of Qun alliance. Many players who did were later indignant, because it turned out they've made a 'not-right' choice - even though there were many red flags when it comes to possible alliance with the Qun or what will happen with Bull.
It's similar with Leliana, or Blackwall, or Cullen, or choices to conscript or ally, or who we pick as ruler of Orlais. And if we choose to do more side-quests or go a longer route (with oftentimes some interesting choice here and there) or choose to befriend rather than antagonize people oftentimes we're rewarded for it with something positive.
I'd be pretty pissed at BioWare for giving me a choice and then obviously favoring one over the other, for playing favorites and picking sides and making things so hopelessly black-and-white.
That's assuming that the choice will be hopelessly black-and-white - it doesn't have to be. Like many other choices it may simply be better than the other. We don't have to go into extremes to pick a better route. It's been like that since DAO - there are certain choices that are better than others.
You have to admit though that so far people who want to kill Solas are justified to do so - he may be a sympathetic antagonist, but he still threatens to destroy the world. It's those who want to redeem him that so far are on shakier, moral ground here; and I presume we may be so throughout most of DA4, with our intentions and loyalty questioned. That in itself makes the redemption path difficult so far. So what is left for those who just want to kill the bastard?
Besides, ideally both routes will be pretty tough for various reasons, to have pros and cons and be roughly equal to each other in those terms. Not just because it'll be interesting to see routes where Solas is framed as a straight-up villain (Imagine comparing low-approval and high-approval Trespasser, only magnified across an entire game) but also because BioWare, and Dragon Age especially, has a nasty habit of presenting you with difficult choices, and then throwing a perfect third option at you no-strings-attached. I don't want that, I don't want it that simple. I want the story to kick me in the ass and tell me it's not having any of my "hero" bullsh-t. Things are far more interesting that way - and as Solas said, sometimes all you have are terrible choices.
Did I say that I want it to be simple? At best I said that I want it to be "easy" - in large quotation marks
And I have no problem with the game giving me an option of a better solution though - especially if that better solution comes from working my ass off and not cutting any corners. That doesn't mean that I don't expect difficult choices even on that route - but seeing that so far we have little information and merely a handful of hints that may suggest that the redemption path is at all possible, it's THAT route so far that is more difficult than the other.