@TimRichmond No official confirmation with regards the amount of games included with Pro sub as of now. As for now it's best to assume that there's no pattern.
@TimRichmond : Still no confirmation one way or the other as to what to expect, also no confirmation AFAIK about what a regular schedule is either. Could be monthly, could be every 5 weeks or longer. I know we are all expecting monthly releases to be added to the Pro list of games, but Google haven't confirmed that either way to the best of my knowledge.
My thoughts on this are that 1) Google hasn't decided any of this yet, and 2) 2 games a month seems unlikely.
I think Google is creating some goodwill right now to make up for a pretty bad launch, and also to reward the early adopters of the platform. But they haven't stated that there will be "pro" claimable games monthly (only "regularly") and haven't stated how many games will be offered regularly.
The reason I say 2 games is a lot is because even after the release of all the games they have contracted so far, it's going to be a relatively small library. And, it's going to be a library packed with newly released games. Game development takes a long time. If they offer 2 free games a month they're going to run out of games pretty quickly unless they find a way to get older games into the platform quickly. And I can't see them offering some of the upcoming newly released games for free when games like AC Odyssey are still full price.
So I think they'll offer free games regularly as they said but it'll probably be one game and honestly I don't think it'll be monthly until they build their library up better.
I think ascribing any kind of pattern or precedent to Stadia this early is a mistake. Google's official position on free Pro games was, as I recall, "roughly one game per month." That could be interpreted in at least two ways: One, that there will be "roughly" one game per month, or two, that there will be one game "roughly" per month.
In other words, some months there may be one game, and other months there may be more than one -- depending on which and how many developers accept Google's terms for free Pro licenses, whatever that may be. Also, the free game(s) may or may not always be on the first of each month; there are some months where perhaps the free Pro game(s) are posted the second week.
After Stadia has been out for around a year will we really be able to figure out any kind of pattern, if there is one.