Well, we're pleased to report that the question has been answered, and the news is good. In August 2020, Deadline reported that Lionsgate CEO John Feltheimer told investors on an earnings call that the studio was "busy preparing scripts for the next two installments of our John Wick action franchise," and that the goal was to "shoot both John Wick 4 and 5 back to back when Keanu becomes available." At the time, Reeves was busy shooting Matrix 4, which wrapped shooting in November 2020 (via Cinema Blend) — and recently, fans received an update courtesy of Ian McShane, who portrays Winston, the duplicitous owner of the Continental Hotel, in the films.
Speaking to Collider in January 2021, McShane said, "I know the script is being written and they're hoping to do it this year. I know [Lionsgate] announced they were gonna do [the fourth and fifth installments] together, but who knows. The studios announce all sorts of things. No doubt, at some point this year, we're gonna do John Wick 4."
It sounds like Stahleski and writer Derek Kolstad, who has written or co-written every film in the series, have a few more sleepless nights in their futures, racking their brains for ways to top themselves yet again. As to whether they'll eventually have to repeat the process for John Wick 6, though, that's an open question.