Wildspace was always the meat of the setting anyway. Spelljammer campaigns were either exploring your own system's Wildspace, or going to other Wildspace spheres to explore. The phologiston was just there, and no one really went there just to go there for itself, but to go through to get to somewhere else more exciting. It served no purpose other than to be passed through. Now they've replaced it with a much more interesting transitive space in the Astral, which is definitely a smart move in the design sense. And a change that's likely to ruffle a minimum of feathers outside the absolute Spelljammer purists, if such exist.
The only remaining question is if you can go from Wildspace to Wildspace without passing through the Astral? Is the Material Plane fully contiguous (meaning you can theoretically travel from system through system, presumably through a large void like our own interstellar space, although distances might be too long to be practical), or is it broken up into discrete and non-contiguous Wildspace systems floating in the Astral? The latter is a bit weird considering how the Material Plane has been consistently described in all editions up until now (as an unbroken infinite plane, or an infinite number of unbroken infinite planes).