I keep telling everyone, looking forward to Solas as an LI is probably a mistake... I don't want to be negative, but I also don't want everyone here to go all squee and gleeee and then be crushed because they can't have him, or worse, they can have him and he turns out to be completely unenjoyable as a love interest when the game is actually released.
They did have Thane in ME2 as an LI who was in his 40s or so, but that was the Mass Effect team (of course... Patrick Weekes WAS on the Mass Effect team...). I have the impression that people in Thedas don't live as long as the people of the Mass Effect universe; if you're in the ME-verse, then you will probably live to around 120 or older (if human), so ten years is not that huge a difference if you're both adults. In Thedas, I'd guess most people don't live much past 70, if they even make it that long, considering what I'd guess at for Wynne's age (I'm guessing at this based on the supposed age of Rhys--probably in his mid-40s--and she considers herself old enough to be long-dead).
I wish he could be, don't get me wrong. His age doesn't bother me, though I'd most likely consider him too old for me if he were a real-world person; I prefer people closer to my own age, but this is a video game. With a certain degree of age differences, people tend to be at totally different places in their lives, wanting different things, at differing levels of maturity or lack thereof. It would be refreshing for BioWare to offer up some 40-somethings as romantic interests, but it seems likely to me that their romances will mostly be in the 20s-30s range, with maybe one or two being early-40s--because that's usually the age range of romances.
But, based on what little evidence we have... Solas is about 99% likely to not be a romance. He talks about "kids these days," for starters--which could include the Inquisitor; we don't know. That doesn't mean he's closed off to the idea, but if he sees the Inquisitor as a child, then being romanced by him/her would become automatically creepy. His age range also seems higher than usual for a Bioware romance--not that I'd object, but BioWare may be presuming a 20-something to 30-something range in their primary audience (since evidence indicates gamers are on average in or approaching their 30s now). We also know that Iron Bull will "sleep with anyone he doesn't think he will break." To me that suggests Iron Bull as the bisexual romance. Dorian is the gay romance. Cullen is the only remaining romance option.
To analyze this further... Solas is all alone, wandering. He's been this way for a long time. If he's in his 40s, maybe he's already had a family, or tried out romance, and it either ended (poorly or otherwise), or he learned it wasn't for him. Perhaps he's asexual and more inclined toward bromance than romance. Perhaps he is romantically involved with a spirit. We don't know. Either way, he's run across other people on his journey and yet he remains alone. You could argue he just hasn't found the right person yet, but you could also argue that he's just not looking for love.
Many have pointed out that Solas is dry, stoic, levelheaded, openminded, etc. and that these are all awesome traits of awesomeness that they'd want in their Inquisitor's LI. The devs, on the other hand, didn't make Varric a romance initially because he didn't really have conflicts etc. set up and they felt he'd be boring as a romance. If Solas is precisely what we want (not really extreme to any end, generally kind, intelligent, stoic, dry, etc. etc. etc.), the developers might have felt he'd be a bland, disinteresting romance because where are his personal dilemmas that will cause conflict to iron out in that relationship? Personally I'd be okay with a "boring" romance, without any angst or personal drama--a single source of stability in a chaotic and unstable world--but most people wouldn't be.
If all of that isn't enough, well... some of his concept art makes him look older, and that gives a more "mentor" or "wise old hermit" vibe, to me.
If Solas is a romance, he will likely be an "extra," or more likely it's Bull who's the extra, but you know what I mean. We do know that there is race gating, and we've been told everyone nevertheless has options. To me this says Iron Bull at least won't be available to any and all, likely he's only available to humans and qunari. So, Solas could be an extra option to make up for the lack thereof for those who can't romance Bull. Or those of us who don't want Iron Bull, or can't have him, may be assumed to have sufficient choice between him and, say, Cullen, or if male, then Dorian. If everyone has multiple options, then there probably are eight romances, with four most likely being bisexual. But the developers only said everyone will have options, not that everyone will have more than one option. I infer that we'll have six and only six until the chart/LI list/whatever is officially released.
Long story short, the more info we have, the less I expect Solas to end up being on the list of LIs. On the one hand, that's sad because no male elf romance (and my Dalish Inquisitor will be celibate)... but it would also be refreshing because really, do all elven companions need to be LIs?
Also, while I took the "just the average elven apostate" line from Patrick Weekes to mean that, well, most elven apostates would not go to the Inquisition during a mage/templar, elf/human conflict, I wouldn't take being told his age to necessarily discount him as potentially an ancient elf. While I think it's more likely he's a standard apostate and exactly what he appears to be, the early-to-mid-40s age might only be his physical/intended apparent age. If he were an ancient elf, the developers would not spoil that for us by telling us he's, say, 3,000 years old or so (I know that's not right but I'm not sure how long ago Arlathan/the Dales fell in the current Thedas timeline).