Yes, you can spend a couple billion designing and building a console that'll have awesome hardware specs the year it's released. But it'll be a year before a bunch of software becomes available for it, and two years before software which starts to really utilize that hardware comes to market. By that time the average PC will be shipping with better hardware, and given the plummeting price of PCs, for not much more money.
Worse, smartphones and tablets are on a yearly upgrade cycle, and allow you to game anywhere - home or away. They can't touch the performance of a brand-new console, but by the time that console gets established the performance gap will have shrunk considerably. And the mobile devices have enormous installed userbases, pulling in equally enormous pools of developers.
The economics of the console business just don't make sense. It doesn't make sense to spend billions developing a new console, it doesn't make sense as a developer to invest millions building games for a risky new platform with few users, and as a consumer it doesn't make sense to spend money on a new console when your PC will be playing better games in a year or two, and your smartphone has an enormous library of games selling for a fraction the cost that you can play whenever and wherever.
Hardcore gamers alone will not support the console business as it's currently constituted. They need the mass market to succeed, and they've lost it.