The last we heard screenwriter James Vanderbilt (Zodiac) was hired to write a fourth installment in the lucrative franchise. Then the writer’s strike happened and not much else was heard. Now it seems that Vanderbilt has turned in his screenplay and the studio thinks the story arc is such that they can split it into two films with just a little more work and film the whole thing all at one time.

Simultaneously shooting multiple installments of big franchises has become increasingly common of late. The Lord of the Rings trilogy was filmed all at one time, as were the second and third films in the Pirates of the Caribbean franchise. Also the two halves of Harry Potter and the Deathly Hallows will be shot in this manner.

Of course, even if this rumor is true there’s no guarantee that director Sam Raimi or star Tobey Maguire will be back for either film. Neither of the two are contractually obligated to return at this point and both have other projects on their dance cards. Raimi’s currently working on Drag Me to Hell for next year and a Jack Ryan reboot for Paramount aiming for summer 2010 release, while Maguire is attached to produce and possibly star in Robotech for Warner Brothers.

The summer movie season got started with a bang as Iron Man exceeded expectations and managed to gross a stunning estimate of $100.8M in ticket sales over the Friday-to-Sunday period, good enough for the tenth largest opening of all-time and the second highest ever for a non-sequel after the $114.8M of 2002′s Marvel Comics sibling Spider-Man.

The film began it’s run with advanced showings at 8 p.m. on Thursday night which grossed an impressive $3.5M in the four hour period before midnight when the official Friday launch started. Added to the weekend gross this amounted to a gargantuan $104.3M in just over three days easily beating out industry (and my own) expectations which were in the $70-90M range. The comic book actioner easily led the box office to the biggest weekend of the year and accounted for two-thirds of all business in the top ten. The film saturated the marketplace this weekend, averaged a stellar $24,543 from 4,105 theaters and an estimated 9,000+ prints.

Overseas box office was almost as generous to the comic book hero. Iron Man invaded 57 territories this weekend and made off with an incredible $96.8M putting the global launch at a humongous $201M since the first international openings on Wednesday. With a reported budget between $140M and $180M, Iron Man should have no trouble recouping its negative cost.

As far as Marvel characters go, only Spider Man has seen a better franchise debut with the first film grossing what would be around $140M in today’s dollars. Adjusting for inflation, opening weekends for other first installments of popular Marvel comics fall much shorter than Iron Man with 2000′s X-Men pulling in $71M, 2003′s The Hulk making $73M, and 2005′s The Fantastic Four pulling in $62M.

Paramount, who distributed the film, is undoubtedly happy as Iron Man was the second largest debut in company history trailing only the $121.6M of last May’s animated sequel Shrek The Third that it released for DreamWorks. The studio’s previous high for a live-action film was with last July’s Transformers (another DreamWorks film) which opened to a Friday-to-Sunday gross of $70.5M after a mid-week debut.

Despite doing so well on opening weekend, Iron Man has indicators that it could have decent legs. Critics and fans alike have overwhelming praised the film. It is currently scoring an unheard of 94% on RottenTomatoes.com which is the best of any wide release this year and is the best of any super hero film EVER. Exit polls by CinemaScore also indicate fans are extremely impressed with the film. It is scoring a fantastic A grade making Iron Man one of the few films that scores highly with both critics and ticket buyers alike. Next weekend will likely tell the tale of how far the film is likely to climb but $250M is well within reach and seems quite likely.

Were you one of the many people who saw the film this weekend? What did you think? Is this the best action hero film ever? Is it better than Spider Man?