UPDATE 1/12/21: PlayStation has now officially confirmed the below leaked selection of PS Plus games for December: Godfall (its "Challenger Edition") for PS5, as well as Lego DC Super Villains and Mortal Shell for PS4.
What is Godfall's Challenger Edition? PlayStation's blog seems to describe it as a kind of trial version featuring three endgame modes - Lightbringer, Dreamstones, and the Ascended Tower of Trials - for which you'll be "immediately equipped with a spread of deadly weapons and skill points, letting you team up with up to two other players in co-op".
You'll play with a mix of people who have this Challenger Edition as well as the full game. You can also choose to upgrade to the full game if you really like what you see.
ORIGINAL STORY 24/12/21: Next month's PlayStation Plus games will include the "XXXXXX Edition" of Godfall for PS5, plus Lego DC Super Villains and Mortal Shell for PS4.
The version of Godfall included in PlayStation Plus appears to be an all-new edition. Is it extra rude? Or is XXXXXX just a codename? We'll find out soon.
Godfall, if you've forgotten, was the Gearbox-published fantasy hack and loot game which arrived alongside the PS5 last year to mixed reviews. (Vikki dubbed it "beautiful but hollow" in Eurogamer's Godfall review.)
Lego DC Super Villains is another fun licensed Lego tie-in from the usual crew at TT Games focusing on DC's baddies, while Mortal Shell is a gloomy Dark Souls-inspired action RPG.
November's PlayStation Plus games - including Kingdoms of Amalur: Re-Reckoning - are still available. Here's the full rundown of those.