Nobody would have prevented them from changing the ToS after a few years to not refund new purchases after date X. It would have been a bad signal but if the platform was successful people wouldn't really mind.

If you put it in from the start it wouldn't be an issue. Or even just guarantee refunds from purchases in the past 3 years. So there is a rolling window and you can lessen the impact but closing the store and continuing operating the platform for 1-2 years.

“We’ll refund the purchases made while the service was in public beta”

Presumably it would be something like "we will refund any purchase if we shut down before 2024" or something like that.

I would have liked this kind of promise, but for the general public this marketing message might have sounded differently: "We might shut down before 2024".

Even if some people are kind of used to this happening, stating it more obviously might have a negative effect just as well.

They wouldn't have to give it a specific timeframe. It could just be a commitment that in the event that they shutdown, they would refund any purchases made within 3 years of their shutdown, and partially refund any purchases made within 5 years.

Just have a rolling refund window - "If we shut down the service in 3 years, we'll give you a full refund, and if between 3-5 years, a half refund".

And then if you need to and don't want to refund, just keep the service limping along for 5 more years.

The monthly subscription costs will not be refunded, only controllers & games you "bought", instead of played via Pro subscription. If Stadia had been a success, there'd been plenty of Pro subscriptions.