I don't think that's the case. It seems that Spiderman is going to investigate that portal up in the sky and gets sucked in. Tony grabs an armor and flies after him. He ends up giving spiderman the armor so that he can run away and stays behind.
It seems the actress was doing some mocap for the movie, so she'll be wearing an Iron Man suit.
It would be an interesting way for Tony to kick the bucket, a self-sacrifice I mean [for either of them or anyone else]. Not that I want him to die, cause I don't. I would like to see him playing a role as one of the Illuminati.
That was my assumption based on the trailer as well. Tony will send Peter to safety in his armor and die at Thanos' hands as a result.
I also suspect Loki will die in the opening moments. Thanos will demolish the Asgardian ship, Loki will sheepishly offer the Tesseract in a too little, too late truce offer and be killed as a sort of symbolic passing of the torch from Loki to Thanos as the Avengers' main foe.
Also, this next part is a semi-spoiler, so skip it if you wish
*** spoiler space ***
I'd read that Joss Whedon had an idea for Avengers 2 where Iron Man in his Hulk Buster armor is battling Ultron and getting pounded. As the armor is smashed, blood begins spilling out, only to change from red to green as it's revealed Bruce Banner was in the armor rather than Stark, and the Hulk bursts out. The scene sounded dope AF but was not used, and I wonder if perhaps it was saved for Infinity War. Would love to see that.