The ars technica article about this has some additional info from the hacker about sony not really being able to do this:
"CTurt stressed to Ars that it would be nearly impossible for Sony to plug the hole that enables mast1c0re. That's because a version of the exploitable PS2 emulator in question is packaged with each available PS2-on-PS4 game rather than stored separately as a core part of the console operating system. [..] For physical PS2-on-PS4 discs, that means the exploit should continue to work as long as you refuse any online updates before playing. And for digital releases, even if the exploit is later patched out, there are methods to downgrade to a stored, exploitable version using proxy HTTP traffic from a local server."
so there isn't just a single PS2 emulator in the PS4/PS5's OS, it's a per-game emulator.
If Sony wanted to end PS2 support on the PS5, my theory is that an easy way for them to work around what is described in the quotes would be to simply issue a new system update which then refuses to run the name of the executable or loading a support library it needs to operate.
I believe it is doable, but the long-term impact to consumer loyalty is another question. Xbox is a peer system and people may move to it and potentially not return.
They also ripped the user-facing Web browser out of the PS5 because "zomg Webkit exploits", despite leaving in web browser features like the online user guides, social media linking, etc, that could all still be used to the same conclusion.
(I'm frustrated over this because as an ISP employee that has to answer to 'slow device speed' complaints, we try to speedtest from the device, and the built-in PSN speed test is woefully low compared to a browser-based test proving our network isn't to blame.)
They also lost a class action lawsuit over OtherOS, needing to pay people that used it $55.
With PS2 emulation, I suspect far more people do use it and it would be much, much easier to prove you used it. This could lead to a huge settlement against them.
"CTurt stressed to Ars that it would be nearly impossible for Sony to plug the hole that enables mast1c0re. That's because a version of the exploitable PS2 emulator in question is packaged with each available PS2-on-PS4 game rather than stored separately as a core part of the console operating system. [..] For physical PS2-on-PS4 discs, that means the exploit should continue to work as long as you refuse any online updates before playing. And for digital releases, even if the exploit is later patched out, there are methods to downgrade to a stored, exploitable version using proxy HTTP traffic from a local server."
so there isn't just a single PS2 emulator in the PS4/PS5's OS, it's a per-game emulator.