for CX, placeholder will be A333 for short-haul or A359 for long-haul routes, except for a few "classical F flights" like CX251/2, which will be 77A assigned from very early on, sometimes even possible from T-365

actual aircraft types are assigned much later, and usually in a number of stages (so no "universal update date" for a particular season);
as a rule of thumb, any changes that result in an extra cabin class available will be updated earlier, say assigning 77A to CX253/4 (such that F tickets will be available for purchase), or deploying an A350 to select NRT and KIX flights (so PEY will be sold); from my experience this year, I started seeing A350s on Japan routes from June-July, for the NW25

other than that, some flights might get the actual aircraft loaded as late as only one month in advance - mentioned somewhere earlier this thread as well

in particular, CX short-haul routes are extremely prone to equipment swaps, I won't be surprised if a KIX flight sees an A333 on Monday, an A359 on Tuesday then a B773 on Wednesday