I really don't think it could be their last console. They could take some pointers from Nintendo and with a little innovation approach gaming from a different perspective. But they have always cut their own path. Console prices cannot just keep going up. Sony cannot price themselves out of the market. I think with the PS5, hopefully, they might realize this. There is a limit gamers will spend before you become a niche market with your product.
Can the whole game industry reach a pinnacle where consoles have nowhere to go? Just where is the tech going? Without widespread access to the internet there can be no cloud gaming. Unless you isolate a segment of the gaming population. What are modern gamers looking for?