An adventure setting spanning the infinite realities of the world’s greatest roleplaying game
It looks like this will also follow the template of the Spelljammer books, with some player options, setting information, and DM facing content (adventure & creature statblocks).
...i think planescape + planebreaker will be the way to go for fifth edition, similarly to spelljammer + the ætherial expanse, but of course there're also always DM's guild reprints to flesh out TSR-specific setting lore...
...i did the math last week with an imaginary shopping cart and calculated that we can get the entire corpus of second-edition planescape material in (re)print for about $300: tempting, albeit pricey...