Hey there,
Google hasn't shared any further details with us but as we understand it, you'll still be able to play Baldur's Gate 3 until January 18, 2023 when Stadia's streaming service officially shuts down.
According to their FAQ, they plan to refund any game purchases made on Stadia by then.
In the meantime, Google has shared this FAQ with more information:
https://support.google.com/stadia/answer/12790109
