Nice to see details, but as expected, I don't think this really justifies the price, which I guess is technically £20, but seeing you can't buy it seperately and it's linked to pricing MM at £50 (which it itself may be debatable if it's worth that), puts things up into question.
Even at that, I'm just gonna keep pointing to other examples. The Witcher 3 is doing this for free and it's 5+ year old game now, so SM, which is a newer game and one published by the platform holder (who you'd think would be trying to come up with ways to entice people to jump onto the newer platform more easily), I haven't seen any real attempts, it's all paid upgrades, except for stuff releasing now, and the PS store is a mess as it doesn't label or even list the games we know of that can be upgraded to PS5 for free if applicable.
It would really depend what SM was doing to justify it, and at essentially full price, I'd be expecting a from the ground up remake for that price, (which wouldn't be worth it), and that's simply where the bar is now, which you'd think Sony would consider seeing they made some of them, like Demons Souls/SOTC/Medievil (kinda), etc.
I don't care about the facial capture, didn't feel necessary to do to me, ray tracing, higher fps, new features I'm all for, but not sure I see it being worth £20+, especially when I already own the game with ~90% of the same content.
I will probably want it eventually, but I don't see it being worth the cost, but sadly if people buy it, they can justify it, so that's where we are with it. Shame Sony is being pretty backwards on this kinda stuff, and we're seeing Xbox giving free upgrades for the likes of Gears 5 and etc.