In the subscriber Q&A section of Mark Gurman's Feb 5 Power On newsletter, Gurman responded to a query about future updates to the Mac Studio, saying: "I wouldn’t anticipate the introduction of a Mac Studio in the near future."
He elaborated that there's a possibility there won't be any Mac Studio refresh at all, or that Apple may hold off until the M3 or M4 chips arrive, presumably in two or three years' time. The reason is that Apple sees the Mac Studio and Mac Pro as having very similar functionality, and therefore wants to differentiate them once the Pro gets updated.
The Mac Pro is for now the only Mac Apple currently sells with Intel chips rather than its own M-series silicon, which has led to amusing situations where the far cheaper Mac mini M2 now outperforms the Mac Pro on certain benchmarks. But with the Pro rumored to get M2 Max and M2 Ultra chips, it should soon regain its spot at the top of Apple's Mac power hierarchy.
Like the original 2019 model, the next Mac Pro is looking to be aimed at the most demanding users. It'll offer room to expand your storage, GPU and other components (excluding RAM, unfortunately), something other Apple Silicon Macs don't let you do, but should still ship in the same cheese-grater-esque tower case.
The Mac Studio comes in a much more compact body than the Mac Pro does, so users wanting the best performance-per-square inch in their Mac will be annoyed if the Studio is stuck with outdated chips for a year or two. The new Mac mini does offer impressive performance, particularly the M2 Pro variant, although it isn't quite as strong on the GPU benchmarks, plus it lacks some of the Studio's ports and can't support as many displays
With the Mac mini M2 and MacBook Pro 14-inch M2 Pro and MacBook Pro 16-inch M2 Pro having just receiving 2023 updates, it's looking less likely that we'll see an Apple spring event this year. Apple could still surprise us with a March showcase of the Mac Pro alongside other rumored devices such as the Apple AR/VR headset, but perhaps we'll be left waiting until WWDC in the summer, or even Apple's September iPhone 15 launch event, to see the Mac Pro debut.