Before I list this weeks games that come included with the Stadia Pro subscription, a general reminder how it works: Stadia Pro is the paid service of Stadia, which includes games you can claim as part of the subscription and after claiming play as long as you are subscribed. That is in difference to Stadia Basic, which is free, but doesn't offer free games as part of the subscription. In both Basic and Pro you can pay for games in the full catalogue to play them unlimited (even without subscription).

With that said, the four new games included starting January are:

• F1 2020
• Hotline Miami
• Figment
• Ary and the Secret of Seasons

Additionally one game is available right now:

• Ctulhu Saves Christmas

Until December 31th you have the last chance to claim Celeste, Dead by Daylight, Embr, Gylt, Risk of Rain 2 and Rock of Ages III. Don't sleep on Gylt, this is a great game.

The following games will still be available through January:

• Sniper Elite 4
• The Gardens Between
• Hello Neighbor: Hide & Seek
• Secret Neighbor
• Republique
• Sundered: Eldritch Edition
• Jotun:Valhalla Edition
• Hitman - The Complete First Season
• Hitman 2
• Gunsport
• PUBG - Breakthrough Edition
• Orcs Must Die! 3
• Crayta: Premium Edition
• Panzer Dragoon: Remake
• Superhot: Mind Control Delete
• SteamWorld Heist
• SteamWorld Dig
• SteamWorld Dig 2
• SteamWorld Quest: Hand of Gilgamech
• Human: Fall Flat
• Lara Croft: Temple of Osiris
• Into the Breach
• Kine
• Monster Jam Steel Titans
• Everspace
• Outcasters
• Submerged: Hidden Depths

source: https://community.stadia.com/t5/Stadia-Community-Blog/This-Week-on-Stadia-Try-Stadia-on-iOS-plus-new-games/ba-p/47623

last month: https://gamrconnect.vgchartz.com/thread/243884/stadia-pro-games-of-december/

So, games are cycled out of the Pro lineup and new ones are brought in? It functions more like Gamepass than PS+ in this regard?

It's the same with PS+. The games you can claim with PS+ regularly change. Similar to PS+, once you claimed a game for Stadia Pro you can play it as long as you subscribe to Stadia Pro. The difference is, that many games stay up to claim for months.

Good lord stadia is still going i fouget it was in it's death bed.

...or is it?