Originally Posted by DyeLorean
The wheels were not in motion during Iron Man, but there was definetely a plan, the seeds of what eventually became The Avengers were already there.
'A plan' meaning 'yeah we want there to be an Avengers movie someday' - not like a single script being polished to perfection over the course of 4 years, the way you suggest.
Whedon was hired in summer 2010 and rewrote the entire script for a movie that came out summer 2012. That's not much time at all.
Saying The Avengers has been being worked on since pre-2008 is like saying Episode I was 22 years in the making.