The expansion after Endwalker will probably be released in Summer/Fall 2023.
I would assume that PS5 install base will be fine then just like the PS4 install base was when they cut off PS3 support with Stormblood.
I certainly hope that's the case by 2023, but I'm pessimistic on next-gen's adoption rate over the next 2-3 years. The demand is clearly there, but we're only expecting to see
some relief in the semiconductor industry by the end of this year. There doesn't appear to be any consensus on when the shortage will end — searching online indicates it could be "into 2022" or as late as 2023.
The expansion after endwalker will be in ~3 years as of right now. If they can't ship enough consoles until then, then the semiconductor industry has far bigger problems. And what is considered a mid-range PC will change also in 3 years
The components that people can afford (or even acquire) today will also have an impact on the makeup of mainstream PC gaming 3 years into the future, and it's pretty grim on the GPU front. Nvidia is re-releasing GTX 1050s and RTX 2060s just to meet demand. Pre-owned GTX 1660s are selling for $100-200 over MSRP. The $329 RTX 3060 will exist for 30
seconds milliseconds on February 25th.
The base PS4 is already struggling and in let's say 3 year, this old machine with an even more outdated CPU will hold the game back even more. The engine doesn't utilize all cores on my Zen+ PC, that's why Limsa is totally unstable frameratewise. And now they have included a 48 player RAID. Bozja alone is incredible if you consider the amount of player in one instance and why should they limit themselves? As if they would just stop there and support a platform for all eternity. They even made the switch from PS4 to PS5 free and I reather see them offering streaming solutions, which would at least make sense for a MMO.
I'm not confident that Yoshi's team would even bother with substantial graphical/under-the-hood upgrades, even if they had the opportunity to cutoff PS4 support, especially
Given Yoshi-P's rejection of any concrete plans for a major graphical overhaul:
Yoshi P said:
By raising the quality a bit higher we may unintentionally exclude people by having such an increased quality. Which is completely defeating the purpose, we want people to enjoy the game. We can't plan for it on a whim, we have to be very meticulous, we have to make detailed plans for it. Including, how are we going to set up our workflow, how are we going to have our pipeline set up, how are we going to code based the deadlines we need to meet? How do we create a pipeline to make a massive amount of assets in the game?
Of course, I'd love to be able to upgrade the graphics at some point but it will require a lot of planning. We're exhausted from Shadowbringers so we want to launch that and maybe then we'll consider our options.
The PS3 was a clearly a limitation on what they could do with the UI and the scope of zones in ARR and Heavensward (especially Sea of Clouds and Azys La, woof), but the PS4 hasn't been a limiting factor for a host of new UI features and much more detailed flying-enabled zones like Azim Steppe and Il Mheg.
On the PC side, the DirectX11 client is the only major update to the game's engine since the launch of ARR, and even though the minimum requirements are nudged upwards with every expansion, the visual and gameplay improvements are marginal at best.
Simply put, Square Enix prefers accessible system requirements (similar to World of Warcraft) to maintain a large player base. Yoshi-P also plays it safe by avoiding anything that could delay their content delivery schedule, like retooling a ton of existing assets (i.e. headwear on Viera and Hrothgar). Is a massive overhaul in 2023-2024 worth dropping PS4 support for an already successful platform that would end within 2 years?