The first tier would be similar to what PlayStation Plus is now (offering a few monthly free games), with the second tier offering a large catalogue of PS4 and PS5 games (presumably expanding on the PlayStation Plus collection). The third tier would include the previously mentioned inclusions as well as a library of PS1, PS2, PS3 & PSP games as well as extended demos and game streaming.
Obviously, PS3 games on the PS5 would be a huge deal. Titles such as the inFAMOUS games, several Ratchet & Clank games, the Resistance games among many others are currently not able to be played on the PS5 or PS4.
It’s unclear if an announcement of this could be imminent or if it’s still months away, but there’s no doubt that Sony is looking at ways to bolster an Xbox Game Pass competitor and this could very well be apart of that.