I know there have been a couple of death flags raised against Armin, especially the whole thing about Armin's dream to see the beach and whether Eren will be the one who ends up seeing it instead of him.
In the most recent chapter, it was hinted that Armin's plan involved more than a little bit of risk to himself. Armin himself realized that he might lose his life carrying out this plan and would therefore never get to see the beach.
BUT I DON'T CARE!!!
If Armin dies, I'll still continue reading this manga and follow the story. But to me, it wouldn't be Attack on Titan anymore.
The main cast of characters made Attack on Titan what it is today. Armin is, in my opinion, the most relatable of all the main characters, and his ongoing character development from wimp to certified badass is what kept me coming back all these years.
If Armin gets killed, this manga just wouldn't be the same anymore...
P.S. Maybe I should have looked at it from a different perspective. Isayama probably understands the importance of Armin's role in the story too, which means Armin would have more plot armor than I originally thought. So please...don't die, Armin.