I live in London, so probably not far from the GCP data centre, I have a 50mb connection (pretty average and affordable for London) and I don't see myself ever investing in a console or gaming PC again.
My gaming experience with Stadia is better than "good enough", and that's all that matters. If they can get the good titles, they have me as a customer.
I would settle for a lower quality service than I'm currently getting before I think about buying my own hardware again.