The main parts of a computer, CPU, mainboard, & GPU are generational, & their prices tend to remain fairly stable until the
next generation arrives, then the previous generation prices tend to fall, which basically means you can buy the latest hardware at high prices, or 'old' hardware for less.
Naturally, it's in the hardware manufacturer's interest to be secretive about when the new stuff will arrive or folks will simply wait for the new hardware, which messes up their sales & cash flow. (which they hate)
Hence, there's no 'right' time to buy. The best you can do is to see what's on offer & decide whether it's price/performance suits your needs & budget.
If you get upset/depressed/angst-ridden when you buy something that's superseded by a new model the week after, then computers are not for you. Consider taking up gardening or something.