With Stadia looking like it's mainly just a streaming service I think what Google would really need to make sure of is that the yearly fee for the service is actually competitive with PlayStation Now and Xbox Game Pass, and they need a large library. The latter aspect will really bite them in the ass if they launch the service with barely anything given PS Now and XBGP have hundreds of games available from the get go (and one rumor I'll keep bringing up until it's eventually confirmed true or not is supposedly Microsoft might be working with Nintendo to bring XBGP to Switch).

My gut feeling with this thing is that it'll just be a bigger-scale Ouya.