So, now Harry at AICN is saying that Stephen Sommers (The Mummy, Deep Rising) is back on G.I. Joe after all. Heck, I Googled G.I. Joe and saw more news reports of this. The rumors of him leaving are based on the fact that the script for the film is bad, not financial reasons.
So, why the rush to get this into production? It's probably for the same reason we're seeing Thor, JLA, and other films rushing to go before cameras recently...
The potential actor, writer and director union (SAG, WGA and DGA) strikes! In 2000/2001, a bunch of films were greenlit because of the feared the SAG and WGA strike that never happened (a deal was reached at the last minute). Hollywood saw a huge amount of production happen in a short time, and they staggered releases, so very few new productions happened for two years or so.
A lot of people I knew were out of work and I could see this happening again. I'm pretty sure new deals will be struck before a strike, but man, a lot of stinkers came out of the last rush to shoot movies. Could Punisher 2, JLA, Thor and others suffer from half-baked scripts? Long post-production times could help, but a bad script is a bad film.
Anyway, back on topic... I wouldn't be surprised if G.I. Joe starts shooting by the new year and we see the film's release delayed a while, regardless of a potential strike.
Source: Ain't It Cool News