This was rumored for a good while under the name "Project Spartacus," and now it's been made official. The easiest way to describe it is it sounds like Sony is taking an approach that mimics both Xbox Game Pass and Nintendo Switch Online. The lowest tier for PS Plus will be PS Plus as it's always been, the regular "pay $60 a year to play online and get exclusive discounts" subscription. The middle tier will be $100 a year and will combine PS Plus and PS Now into one, basically dropping the PS Now name in favor of just making it a tier for PS Plus (PS Now is a service where you can stream or natively download select PS4 and 5 games at no additional cost). And finally the highest tier, the one most akin to Nintendo Switch Online, is you'll get everything from the other tiers, but will also be able to download emulated versions of games from the PS1, 2, and PSP. PS3 is sadly still only playable via cloud streaming, which of course has gotten negative reactions, alongside the fact the price of this tier is $120 a year, double what a basic PS Plus subscription costs (I mean hey Nintendo got flak for the Expansion Pack tier of NSO being $50, of course Sony will catch similar flak for tier-3 PS Plus subscriptions being $120).
Sony's plan is to "roll out" the service by region over the course of 2022, starting with Asian territories in June and I guess places like the Americas and Europe by late summer or early fall.
Now my personal opinion: I can't deny that the inclusion of PS1, 2, and PSP titles in the highest tier has me super intrigued, but I really need to see what Sony plans to add before I even think about paying an extra $60 a year for PS Plus. It obviously needs first party titles like Ratchet and Clank, Sly Cooper, Ico, Ape Escape, and the like, but also third party stuff like most of Square's PS1 output, Tomb Raider, Crash and Spyro need to be there after they were mysteriously not on the infamous PS1 Classic, and if you're not gonna remake Medieval 2 just put the original on the service.