In an interview with Popverse (which will be published later today), long-time Marvel costume designer Graham Churchyard gave a possible sneak preview of what might be next in the Marvel Cinematic Universe.
When asked about how he approached designing a new Marvel Universe (Earth 838) for Doctor Strange: Multiverse of Madness, Churchyard responded, "Apart from the usual things of a script and director and all those endless meetings you have deciding what things look like, Marvel was taking on different worlds. In the beginning, they were trying to create the Defender world, or the 615 as we called it, which was a different Strange from a different multiverse."
"Everything was for Marvel to create different worlds, and they were interested in exploring 838. As I understand it, there were going to be other movies," he points out, hinting at some plans that Marvel Studios either had or have for the expansion of Earth 838. As he says, "If I've got my math right, the last 29, including this one, are set in 616. I think that we've never known anything else but 616, so [Marvel] was experimenting with an alternate universe to take that forward into another phase."
Of course, just because Marvel Studios was interested in expanding into 838 doesn't necessarily mean that's what is on the roster now, however, it definitely suggests that Marvel might extend the universe that we got a glimpse of in Doctor Strange instead of letting it fall to the wayside as the next phase moves forward.