It's for the best really.
Doesn't make any sense to just abandon a platform that's still thriving and profitable.
Hardware sales may be slowing down (Covid boost aside), but they're still making a killing off software.
Most of the games that they already had in development for the PS4 that were scheduled to release post-PS5 launch should be cross-gen since it would make the most sense to start the transitional phase of your user base onto the next platform while also milking the cow of your last platform for every last drop it's got.
That said, I do think they could have done a better job of giving the PS5 a stronger launch and giving their user base a bigger, more urgent incentive to make the jump. But, given the circumstances, I'm willing to cut 'em some slack.
Hardware Comparison Threads:
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Is Hardware Getting TOO Powerful?
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PlayStation/Xbox/Switch: 2022 Edition
PlayStation/Xbox/Switch Hardware Battle: 2021 Edition!
PlayStation 4/Xbox One/Nintendo Switch: 2019 vs. 2020
PlayStation 4/Xbox One/Nintendo Switch: 2018 vs. 2019
PlayStation 4/Xbox One/Nintendo Switch: 2017 vs. 2018
PlayStation 4: 2015 vs. 2016 vs. 2017