It is unfortunate, but hopefully necessary to ensure the health of F to other destinations. It was never sustainable for routes to be filled mostly with partner award travelers!
A while ago, people on here posted that at least 5 of CX's original 53 77Ws were being returned to lessor. I know at least one or two already went back. That F capacity was already removed from short-lived DUS, ZRH, and now ORD. But I also think there is slack in the 77H/A fleet, if my math serves me correctly (long-haul F destinations following the upcoming schedule change will be JFK 2x, LHR 2x, LAX 2.5x, SFO 1x, BOS 1x, FRA 1x, CDG 1x, MXP 1x). Although CX884/885 would seem like an obvious candidate for a cut, especially since 77G/K has served the route before, I think one reason it remains is that it does "alright" if not great, and has an unaligned timing (early evening arrival) which helps make the rotation more efficient. Most of the F-equipped planes are early-morning arrivals. Those planes are lower density / lower yielding than other birds on regional routes, because CX doesn't sell F. Yet another reason 77K/G and the A350s are better for CX, in this new world where F isn't sold or bought regionally, 3-class longhaul planes are more efficiently sold for the daytime regional routes too. Since they don't waste a whole section dedicated to massive F seats which are unsold, or used as J overflow.)
The 777X is going to be badly delayed. My parlor-room suspicion is that while CX may return F class planes to lessor as the leases expire, CX isn't going to convert the 77H/Ks to 77G/K. I doubt they're anticipating flying the 777X meaningfully until 2022 or later.