And now I get around to here to post a much shorter, more condensed version of things I already said elsewhere.
Lorna kept the hell away from Havok in the teaser art is good. I'm also very glad she's in her iconic costume, because it represents her and will help her stand out a lot more for people looking for her (e.g. fans of a certain interpretation on a certain show). That she's included in the event at all is a good thing, though a part of me wonders if "every remaining mutant on the planet will come together" is the reason. Marvel objectively looks bad if they make such a claim and don't include her.
Final visuals note: Lorna in back, Havok at front. I saw the "fliers in back" reason, but Storm and Jean are up front too and they fly. My conclusion is that Marvel is showing they think Havok is important and Lorna isn't. And Iceman and Angel being in the back too aren't enough to make me think otherwise.
Then the details.
"Where the series goes from there depends on who is left standing!" So, character death, which superhero comics suck at hard. I already don't like the event given that detail. Insofar as Lorna is concerned, I'm expecting she'll be killed off. Hell mode: killed off to promote Havok. Lorna's treatment on Blue already shows Marvel thinks her primary value is to benefit Havok. Killing her off for that purpose would just be Marvel taking their bias against her all the way. And I think people at Marvel would convince themselves that killing her off is "acceptable" after they "technically" satisfied giving her more of a presence in the past year via Blue, even though that presence wasn't using or respecting her much. Last time they gave her as much presence as Blue was Secret Wars, and they followed that up by throwing her into forced limbo for two years. There's also how Gail Simone said she thought pitching a Polaris solo would be a "hard sell," which in light of this announcement makes me ponder if she said that because she knows Marvel's going to kill Lorna off.
In the end, we don't know anything for sure yet. We need more details. Anything said right now is pure speculation. However, I base the above speculation on historical and recent treatment of Lorna to make educated guesses on what's likely. They may not be pleasant, but I would rather be prepared than exclusively follow hopeful thinking - which other users cover more than enough to balance out anything I say - and get blindsided.
I certainly hope Marvel proves my guesses wrong.