Well there's the super slim possibility, that the lack of PS4's is due to a new super slim model coming out. How it wouldn't have leaked by now seems impossible, but regardless this is pretty unlikely based on the shortage scenario. Any capacity SNY may have had lined up with TSMC for PS4 7nm APU's would likely be better diverted to PS5 APU's instead.
SNY has no choice but to take the long game into account, and because of that, even if they felt they could profit more off of PS4's right now, they had to make sure not to potentially let XB Series consoles get too much momentum. A weak start to a gen just causes bigger headaches that drags on, and SNY definitely remembers what it was like when they gave XB 360 a year head start. Since the XB Series consoles are proving stronger for MS than both XB1 and XB360, SNY has to keep PS5 at the forefront, even if that means sacrificing future PS4 sales.
