It's likely, but less clear, whether the film will wind up as the top-grossing film actually released in 2014; The Hunger Games: Mockingjay, Part One has long been expected to outdo Guardians at the domestic box office and still may.
Something similar happened last year, when Iron Man 3 spent months at the top of the yearly list, only to be unseated by The Hunger Games: Catching Fire, which weighed in at #3 (behind Iron Man 3 and Frozen) at year's end but went on to generate a crucial $25 million in January and February of this year.
What makes it somewhat harder to judge is that this year's biggest movies have been somewhat depressed overall compared to last year's. Guardians' $332 million would have had it closing out the top five last year, rather than leading the pack, and after five weeks of release, Catching Fire had generated about $80 million more than its successor has to date.
Crunching the numbers a bit, that's roughly 22% of the film's total take and if you extrapolate that over the 19-week release schedule of the previous Hunger Games installment, you get $329 million -- $3 million less than Guardians has at the moment. It's also arguable that the film is descending at a slower rate than Catching Fire, though, and so might end up with more than that 78% of the total, assuming it remains in theaters for the same amount of time. That seems unlikely, though, since while it may not be dipping at the same rate statistically, the bottom-line dollar amount is already lower than Catching Fire was earning in week five. Exhibitors, then, may be somewhat less likely to carry it for as long.
Another complicating factor is The Interview. Last year, Catching Fire saw a bump over Christmas and New Years that helped contribute to the film's long-term success. Given its teen-targeted appeal, it's easy to speculate that's because audiences were out of school and college students were back home for a while. The Interview was targeted at a somewhat older audience -- early '20s rather than teens -- and skewed male rather than female, but it will be interesting to see whether other big titles divvy up that movie's intended revenue now that it's been cancelled, or whether the audience will just stay home.
Should it lose out to Guardians, it's worth noting that Mockingjay did very well considering what it had going against it; movies that are split in half to make a bigger overall buck sometimes take a little bit of a hit in the "Part 1" half of the finale, with some moviegoers skipping out, either out of disgust, or because they figure they can catch up on home video, or with the intention of catching one of those AMC Theaters marathon screenings that finales tend to get (one of those might tease up Mockingjay Part One's final numbers, too). The final chapter is generally the highest-grossing of the lot, though, so look for a big number next year -- although a November release ahead of December's Star Wars: The Force Awakens may not have the longest legs.
It also opened the week after Interstellar and many IMAX providers opted to stick with the record-setting Christopher Nolan space epic rather than handing the screens over to Mockingjay in its opening frame. That means the higher ticket prices from IMAX were forfeited in the film's opening weekend and many of those most likely to spring for the extra few bucks had already been and gone by the time it started playing on a lot of the premium-format screens. That's one of a number of factors credited with depressing the opening-weekend take for the film, which failed to come close to either The Hunger Games or Catching Fire.
Of course, Guardians of the Galaxy is generally expected to earn at least one Academy Award nomination in a technical category. It wouldn't be totally unheard-of for Marvel to do a modest re-release of the film to appeal to Academy voters (they did something similar with Marvel's The Avengers over a holiday weekend shortly after the film was out on video). Even a modestly-successful curtain call -- say a $3 to $5 million weekend -- could shift the numbers significantly in favor of the film most analysts were calling Marvel's biggest risk since Iron Man.
The Hunger Games: Mockingjay Part One had one of the year's biggest openings and paced ahead of Guardians of the Galaxy for its first four weeks, but Guardians had a level of audience enthusiasm that no other movie has had this year, and managed to keep its grosses up over time, ultimately overtaking a number of films with stronger openings along the way to being the current top dog.
In fact, the film is doing better at this point in its release than Catching Fire was; the second Hunger Games film was pulled from theatrical release after 19 weeks when its weekly gross was less than $100,000, while Guardians just capped off its twentieth week in release with a nearly $250,000 box office.
It appears likely that in the next week or two, Mockingjay will dip to the point where it's drawing lower numbers than Guardians was at the corollary time in its release (Mockingjay started out massive but has had bigger week to week drops than Guardians every week it's been in theaters), and that's the point where things will get interesting for math nerds trying to project just where things will go.