Diablo 4's seasons will keep running after Diablo 5 launches, its director says
Game director Brent Gibson told Icy Veins that Blizzard plans to keep making Diablo 4 seasons for as long as players keep showing up, the way Diablo 2 and 3 are still supported. Diablo 5 is due in spring 2029.

Blizzard announcing Diablo 5 put an obvious question in front of everyone still grinding Sanctuary: how long does Diablo 4 have left? Game director Brent Gibson's answer, given in an interview with Icy Veins, is that it is not on a countdown at all.
What he said
"If you're worried, don't sweat it," Gibson said, according to VGC's report of the interview. He framed the plan around player numbers rather than a fixed end date: "We are planning on supporting seasons as long as the community continues to show up for Diablo 4, similar to what we have in Diablo 2 and Diablo 3."
That comparison is the load-bearing part. Both older games still receive periodic attention years after their sequels arrived, and Gibson's framing treats the series as one shared universe rather than a relay race where each game hands off and stops. He also told Icy Veins that an Amazon class is on the way to Diablo 4.
How much runway that is
Diablo 5 is currently slated for spring 2029, so this is not a promise about next year — Diablo 4 has several years of planned seasonal content ahead of it before the sequel even arrives. The open question is what the cadence looks like after that point, and Gibson did not commit to a specific schedule for the post-Diablo 5 period.
Why it matters
Live-service ARPGs live on the assumption that your stash will still matter next year, and a sequel announcement is usually the moment that assumption starts to wobble.