I'll throw my rumor theory into the ring
Nikon is holding back the Z9 firmware until Canon & Sony both announce/ship their new flagships so as to steal some of the hype and convince the weak-willed not to jump ship. Guessing we'll see the FW after Nov 20 and before Christmas, and if we're lucky, before Black Friday/Cyber Monday... so next week.
Z8 will get nearly the same updates, but will NOT get RAW PreCapture due to heat management of the smaller body, whereas the Z9 is built for it. Potentially the Z8 will get PC in HE or HE*, but at the same time I don't believe Nikon will do a half-baked solution. Sorry, Z8 owners, but at least it'll get AF improvements though!
Going forward, I feel they'll begin to differentiate the lines more: Z9 II will drop to 24mpx, get GS and the top-tier AF so as to compete with the other flagships, while the Z8 II will stay in the 45mpx realm with the standard ES implementation we see now, but will be a smidge behind the Z9 II in terms of overall performance (AF, FPS, etc)
Or, Nikon stands pat, lets S and C pull further ahead, and then shocks the world next year with all new bodies with these features.