The rumors were true: Sony is indeed removing the ability to buy PS3, PSP, and PS Vita games from the PSN Store when accessing the via the mobile app or web browser. According to official emails sent out to PlayStation Network members titled “Important Changes to PlayStation Store”, the PlayStation Store overhaul will take effect from October 21, 2020 to October 26, 2020 on web, and by October 28, 2020 on mobile app.
Also included in the purge is the ability to buy Apps, Themes, and Avatars, and the Wishlist feature. Current wishlists will be discontinued. Not all is lost, though: Direct device-based access to the PSN Store through a PS3, PSP, and PS Vita will allow players to buy games. Similarly, accessing the store through a PS4 will surface apps, themes and avatars just like before. Any previously purchased content will be accessible as before.
Here’s a screenshot of one of the emails sent out by Sony about the PSN Store changes:
In essence, the main difference between the official announcement and the rumored emails that circulated last week (which were targeted toward developers and partners) is date of the changes to the web PSN store: October 21, 2020 instead of October 19, 2020. The mobile rollout remains the same. This means that players wishing to easily access some of the remaining content on the older platforms are advised to pick up what they can before then.
Most likely the store overhaul has to do with preparing for the new version of the PSN store that will launch with the PlayStation 5. The PS5 will also debut a new user experience, one with a more closely integrated store. In a surprise State of Play video uploaded on October 15, 2020, parts of the user interface on PS5 were detailed, centered around “cards” and an instantly accessible “control center” function.
The PSN Store will be overhauled on October 21 through 26, 2020 on web, and on mobile app on October 28, 2020. The PlayStation 5 will launch be available in  Australia, Japan, North America, and South Korea on November 12, 2020, and worldwide on November 19, 2020.
