We just got 10.4.9 so I would not expect 10.5 until a) 10.4.10 was released to fix all the bugs of the latest release, or b) after the 1st of the year. Why be so anxious about 10.5?
Keynotes about iPhones, Apple Watches, and iPads never have anything to do with FCPX, so I don't get how that correlates. Keynotes almost never announce new FCPX versions.
Yeah, latest macOS, latest app versions, and I just make a boat-load of money doing actual work, rather than sitting on my hands waiting for a new version that won't make much difference to my daily work life. Not frustrated at all.
Just what would a 10.5 do for you that you need it to be released immediately if not sooner?
I use all sorts of FCPX iterations across multiple OS versions and it hasn't cramped my productivity. If your stuff is dry now waiting for FCPX11 might be the ticket to bring your stuff to life.