Honestly, with game as a service model I can see a console selling that much. For example, with PS+ subscriptions, there is no reason for Sony to stop selling PS4s, they can just keep selling it and releasing slimmer versions over time, every new PS4 owner is a potential 60 dollar per year revenue for them, not to say that its also a likely ps5 buyer. If Sony can have the PS4 for around 100-150 dollars in a few years, it can still sell well for a while, have much more legs than the PS3 had for example. I don't think the PS4 will sell that much, I'm just using it as an example.