Why not, I'm jumping on the cliffhanger theorizing 'cause why the hell not?
In short, I don't believe Orion is dead or that he will die. A few reasons for that. #1 is that this would be a pretty shitty story if the MC died halfway through. This isn't Game of Thrones, so the story isn't built to have those kinds of twists. Everything in the story revolves around Orion, and even Nancy says he's "the glue holding everyone together". There's too much going on for the story to just gun him down and leave it at that. That's just me thinking about storytelling logic that I don't think would kill him off.
#2 is there's no real confirmation that he's dead. Idrial says she can't control/foresee what happens in the "real" world, only in Eternum. I think she's just looking at it as death is the most likely outcome, but nothing is set in stone. This is a cliffhanger and is meant to keep us guessing on an exciting turn of events with no immediate outcome. Nothing new there, it happens every update.
I don't think we're going to swap for a "different" Orion, which would gain nothing for the story and loose the investment we built with "this" Orion. I think he's going to survive in an unexpected way. Honestly I think Calypso is going to have a hand in saving him. We know that the worlds in Eternum actually exist in sort of multiverse way, and we know Orion has a special connection with Cali. He's been able to summon her at Warthogs and has been able to access his abilities in the real world. So far just with his reaction time, but that's part of his powers in Eternum. Cali's tried to use exit portals or summon her own portal to the real word in the past but was unable to do so. Orion has also crossed into Eternum on his own appearing in front of Cali. I think that somehow the two are going to be able to connect and pull her over, being the person with the powers needed to heal/save him.
Also as to why I think its very unlikely that Orion dies there, does anyone remember when Luna touched Annie's hand and had a vision? One that made her look between Orion and Annie, the immediately look down at herself and blush? Doesn't take a genius to figure that one out. She at the very least saw those two doing something intimate, but I think it involves all three of them. She wasn't angry or hurt, just surprised looking at herself saying "there's no way that can happen". Can't have something like that is one of them is dead...