Well, given the title of this review, you'll know that it will be filled with spoilers.  But I'll put the warning in anyway:

[Spoilers ahead ... ]

So, the episode ends with JJ and Luke being caught in an explosion, their communication cut off, and everyone else looking horrified back in Washington, DC.

The main options are 1. JJ dies, Luke survives; 2. Luke dies, J. J. survives; 3. both die; 4. both survive (in the interest keeping this review not overly long, I won't into the possibilities one or both being badly hurt, and how badly).   Let's look at each of these four main possibilities:

1. JJ dies, Luke survives:  This would have the most dramatic punch.  JJ and Penelope are the only characters to have been on Criminal Minds in each of the 16 seasons so far, and JJ was a main character in the first season, in contrast to Penelope, who was listed as "also starring".  Also, even more important, in this episode, JJ promises her husband that she'll call him from now on before she enters a life-threatening situation -- that pinky-swear promise would give her death maximum dramatic significance. (The promise also happens after he finds out he's not suffering from cancer, and we may find out in the future that he was not telling JJ the truth, which would make JJs death now even more devastating.)  But I sure hope that doesn't happen.

2. Luke dies, JJ survives: Not as significant a character as JJ, and he didn't make anyone any promises beforehand.  But his death, as would JJ's, would show viewers that Criminal Minds: Evolution isn't fooling around this season.

3. Both die: This would not much more dramatic effect than just JJ dying, but it's unusual to have two major characters dying in the same scene (other than in Game of Thrones), and this would certainly demonstrate that Criminal Minds this season is going for broke.  Still, I would rate this outcome as the least likely.

4. Both survive: This, to some extent, could have the result of viewers not taking Criminal Minds as seriously as we should.  It would have the least dramatic impact.  But I would say it's the second most likely, after J.J dying, and, as a fan of the show, it's the outcome I'd most like to see, softy that I am.

We'll find out what happens on January 12, 2023, when the series returns, and I'll be back here shortly after that with a review.

See also Criminal Minds: Evolution 16.1-16.4: Outstanding!