If you want to know whether the market is shrinking or growing, look more at software sales/revenue and less at hardware install base. But the more data you look into the better. Any individual metric will be misleading.
PS4 traditional software sales beat DS + Wii's combined, and PS3 + X360's combined. PS4 also has a massive f2p/mtx spending that beats its traditional software sales and completely dwarfs the 7th gen. PS4 remained a big platform years after PS5 launched. Looking at hardware data alone doesn't demonstrate this, rather it implies that PS4 instantly died after PS5.
PS5's popularity as an individual console will be a lot harder to estimate. Because Sony is combining its numbers with PS4 right now, and will combine them with PS6 in the future. Extrapolation is getting trickier over time.
I honestly don't care if the console market is shrinking. Handhelds/hybrids and PC are legitmate alternatives. If PC is the reason why the "console market" is shrinking, I'm okay with this.
