I'd just like to add: I so hope this means there's a Spelljammer thing on the way. Spelljammer is just so delightfully bonkers.
I'm betting they won't go full Spelljamer, but an upcoming adventure will use elements of Spelljammer as part of the story (probably with PCs riding in a spelljamming ship to go to a certain location). If we're lucky, it'll provide some basic spelljamming rules that we use with older material (but I'm not sure that we'll see that, unfortunately). I seriously doubt we'll see SJ races (like Giff and Scro), but we'll probably get some SJ monsters. We'll probably see gith races and psionics/mystic class as part of a companion product, or in the adventure itself (like PotA).
I'm betting they won't go full Spelljamer, but an upcoming adventure will use elements of Spelljammer as part of the story (probably with PCs riding in a spelljamming ship to go to a certain location). If we're lucky, it'll provide some basic spelljamming rules that we use with older material (but I'm not sure that we'll see that, unfortunately). I seriously doubt we'll see SJ races (like Giff and Scro), but we'll probably get some SJ monsters. We'll probably see gith races and psionics/mystic class as part of a companion product, or in the adventure itself (like PotA).
At the very least, they may open up the DM's Guild to Spelljammer!
In regards to psionics/the mystic class, are we close to it being released yet? Mearls did mention that new classes go through a testing cycle of a few years. I think it was as much as 3-5.