That's Lucasfilm's internal date.

When will there be a new Indiana Jones movie? We all know it's just a matter of time, and we can only hope that time is used to get it right. But it's coming, whether it's aged Harrison Ford or strapping young Chris Pratt or someone else, there will be new Indy. 

Sources tell Ain't It Cool News that the next adventure of Indiana Jones has been penciled in by Lucasfilm for Q4 2018. That's internal thinking, not a hard date, but it tells us one thing: Lucasfilm, having started the Star Wars machine successfully, is turning their eye to Indiana Jones. 

Producer Frank Marshall sorta denied it, telling Slashfilm “We’ve had no discussions on ‘Indy 5′ to date.” But here's the thing: I don't think this invalidates AICN's info. It's very likely that Kathleen Kennedy - who has already said there have been internal discussions about the movie - is simply putting the film on internal calendar to get all the Lucasfilm people prepped for the real first stages, which would include talking to Frank Marshall. The modern franchise movie making machine works in ways that are not always obvious, and marketing and merch and logistics people will probably be the first to get information about the amorphous concept of Indy 5 happening. It's up to Frank Marshall and the writers and directors and people like that to decide what Indy 5 is, but it's these Lucasfilm suits who decide that it will be. 

This doesn't mean we should be clearing out our Q4 2018. That's just the date Lucasfilm has marked internally, and it allows them to set other dates for milestones towards production - hiring writers, breaking a story, deciding if it's old Indy or a reboot - which means it's a date that could shift. But for me this indicates that Lucasfilm has kickstarted the Indiana Jones machine, and that we're going to be hearing much more about the return of the franchise in the next year or so.