They have come out and said all first party games will be day 1 game pass I'm pretty sure. I could be wrong though. I guess technically they could go back on that but I wouldn't see the point in doing that. Seeing as how trying to get a quick cash grab on elder scrolls is most likely less important to them than building up game pass.
Agreed, there's no way in hell they don't put those games on Game Pass, Day 1.
Could they? Of course. Would they? Almost certainly not, they would look like total fucking hypocrites and liars.
They don't because it would be bad business. The number of sign-ups who maintain a subscription on Game Pass for a single game will vastly exceed the revenue over even a relatively short period.
Skyrim sold 13.7m copies on the Xbox 360. Apparently some ~4.2m copies sold on the PC. That's nearly 18m. Not all of these were sold in the first year, but the user market has only been growing.
So let's say 15m of
TES:VI sells on the XSX/XB1 and PC platforms in the first year. If that were pure retail we're talking about $1.05bn revenue.
Let's say half of these are gamers who opt to subscribe to the Game Pass service to play the game: 7.5m. Why wouldn't they? That's so attractive. You can pay $70 to buy it, or can pay as low as $10/mo per month to play it. Many gamers are probably thinking they'll be done playing it after several months. Furthermore, the vast majority of Xbox gamers will be thinking, "I already pay $10/mo for Xbox Live, so upgrading to GPU is really just a $5/mo premium for me. At that effective cost, I could subscribe for 14 months before I'd equaled the cost of buying the game."
We'll assume the majority go for this Game Pass Ultimate value because it's cheaper for Xbox users to get that service for the Xbox Live inclusion than to buy Xbox Live + Game Pass Xbox separately. Xbox users also make up the majority of buyers, obviously. Let's assume 75% are Ultimate subscribers ($15/mo), and 25% are lesser PC or Xbox subscribers ($10/mo). Not everyone will be paying the retail subscription rate, but let's assume they do for simplicity's sake.
How many do you think burn through the game in a single month, and immediately drop the service? Probably not many. Meanwhile, you might assume that 10% keep the service indefinitely after subscribing. That 10% are going to yield $10m/revenue a month in perpetuity, or $120m per year. The other 90% will yield $90m in the first month, and every month thereafter, or a rate of $1.08bn per year. Altogether, we're assuming this 7.5m subscriber base is yielding $100m/mo.
Keep in mind we're just assuming half the base went with Game Pass. They've already netted $525m from standalone sales, so the target for comparison is the opportunity cost of $525m. That means that six months membership across the entire base will yield +$75m revenue. Even if many don't like the game, or don't go out to six months, you have that 10% you retain will themselves produce more revenue after 4 1/2 years.
Even if you factor in the wisdom of the consumer, which is that Microsoft would have been netting Xbox Live revenues from most of those users, anyway, you can see why corporations are crazy about subscription services. It's perpetual income. It's a never-ending river of money.