Iron Man was the Patient Zero of the Marvel Cinematic Universe. The nascent film studio's first inklings of a huge, interlocking bunch of franchises came in the big screen adventures of Tony Stark, which did something that Hollywood blockbuster series rarely do: actually established some in-universe continuity. So in Iron Man 2, references to the events in the previous film weren't just winks and nods to audience members who'd actually bothered to watch it; instead, you had the sense these characters were actual people with actual histories and everything they did mattered. So Iron Man 2 further developed Tony and Pepper's relationship and the government's relationship with a rich dude having a fly war suit, and Iron Man 3 dealt with the PTSD-like fallout of the character's involvement in Avengers. Which means that, considering Extremis was such a big deal in that third film, to have it completely absent from the fourth would not only be annoying, but also not in keeping with the rest of the series. And consistency is what Marvel Studios is all about. The technological virus has cropped up in the comics a few times since its debut - sometimes as the focus of storylines, sometimes just incidental - and we'd be disappointed if Iron Man 4 didn't follow suit.
Tom Baker is the Comics Editor at WhatCulture! He's heard all the Doctor Who jokes, but not many about Randall and Hopkirk. He also blogs at http://communibearsilostate.wordpress.com/
