I am serious. But before I get into why I chose $500 million, some comps.
Ant-Man 2015 $519 WW ($180 US/$339 Intl)
Guardians of the Galaxy 2014 $773 WW ($333 US/$440 Intl)
Suicide Squad 2016 $720 WW ($314 US/$406 Intl)
Godzilla 2014 $529 WW ($200 US/$328 Intl)
Mission Impossible: Ghost Protocol 2011
$694 WW ($209 US/$485 Intl)
Big Hero Six 2014 $657 WW ($222 US/$435 Intl)
So we have a mix of films with which to predict Rogue One's potential against. Four of the films are the first entries in a series connected to a larger franchise similar to how R1 is the first Star Wars Anthology film. They all performed well for their respective studios, with SS and GotG performing quite well thanks to strong hype that had follow through. However, $700 million shouldn't be the marker to judge R1's success because those films are at the higher end of successful first entry branded films. Both films also had outsized success thanks to weak competition before and after their release weekends which drove demand. Ant-Man and Godzilla 2014 are where Disney/Lucasfilm should set the expectations for R1. Both were well received entries in their respective franchises which both have sequels in development. Ant-Man in particular is a good comp for R1 because they both came after their franchises' respective marquis entries. Half a billion, even if the film doesn't recoup all its costs in theatrical, is on a good path for future revenue streams like Home Entertainment and Moychendising.
The second set of films came out during the holiday season; Opening around Thanksgiving to around Christmas. R1 will be one of the biggest films this holday season, but its release won't benefit from being considered a cultural event in the way TFA was. That, even if we were to discount China which is necessary with SW, will ultimately be what sets the worldwide gross. R1 will be one of the big Hollywood tentpoles coming out during the holidays as theaters around the world have to determine how many booking they should schedule for the concentration of films that open within a 10 period. Therefore, Ghost Protocol and Big Hero 6's success represents the ceiling for R1's worldwide gross, but...
Then there's the China problem...
China Grosses
Mission Impossible: Ghost Protocol $101 China ($694 WW)
Godzilla 2014 $77 China ($529 WW)
Guardians of the Galaxy $96 China ($773 WW)
Big Hero Six $83 China ($657 WW)
Avengers: Age of Ultron $240 China ($1,405 WW)
Ant-Man $105 China ($519 WW)
The Force Awakens $124 China ($2,068 WW)
Zootopia $235 China ($1,023 WW)
SS aside, the importance of China in the international film market place cannot be understated. As far as I am concerned, TWDC should realize that the MCU is China's Star Wars and accept these new Star Wars films may not do as well as their other brands do over there. Disney has every reason to try to make Star Wars more popular in China, but the Chinese are not stupid and they can smell China pandering a mile away. (See Iron Man 3 China edition) Donnie Yen can't save a film from disinterest on the part of Chinese audiences. But in terms of a specific prediction for Rogue One, Ant Man again provides a good indication for its performance. Ant Man made less than half of what Ultron did, so it's reasonable a similar drop will occur with TFA and R1. ($50-60)
"It's Still Maui Time!" or Canabalism
Last Fall, The Good Dinosaur became Pixar's first financial failure at the box office. While TWDS typically gives its tentpoles promotional breathing room so each one can recieve the maximum amount of possible attention from the moviegoing public, The Force Awakens sucked all the oxygen out from The Good Dinosuar. Nobody didn't not know a new Star Wars movie was coming out, but many folks didn't know a Pixar movie would be in theaters on Thanksgiving. Why keep carpet bombing the public with Star Wars ads when it would be financially prudent to invest in increasing public awareness/interest in the film that clearly could use those resources? As Disney has wratcheted up its branded tent pole strategy, these films can be too close to each other leading to one or more films to underperform or bomb. For example, this past Summer saw TWDS release 4 tent pole pictures, Civil War, Alice 2, Dory, and The BFG, in a two month period. It was decided that Cap and Dory would get the lion's share of the attention resources because they were seen as more important while the other two were essentially allowed to fail. (Political/critical concerns also played a role) This fall, Disney will release three major tentpoles within 43 days of each other during the most crowded season of the theatrical calendar. Not a single one of these films can't afford to fail in the ways Good Dinosaur, Alice, and BFG did and won't. However, that doesn't mean they wont eat into each other's grosses. The audience might give Moana a cultural moment much like Frozen had over its theatrical release and Rogue One will have to perform against that in a way tentpoles released in the spring, like Zootopia or Jungle Book, don't have to.
To wrap up, Bob is doing the right thing by correcting financial expectations for Rogue One, but the number by which it should be deemed a success, and its likely performance, should be in the $500-$600 million range. Rogue One is going against strong headwinds including historical comps for first entry/holiday films which rule out a worldwide gross higher than the low $700 million range at best, the lack of strong interest from Chinese audiences, and Disney having to balance three large tentpoles during a crowded holiday season.
Addendum:
Strong performance in Europe could help make up the difference for the poor performance in China, but by how much is an open question.
Don't underestimate the difficulty for Disney in selling a Star Wars film that isn't part of the main series.