I don't think the cost of developing and supporting virtual machine backward compatibility on consoles is justified. One thing Apple does well is drop support for old stuff and it hasn't hurt their business much at all. In fact, they doing very well without it. I think the expectation that a gaming console will remain backwards compatible with completely different older models is not realistic. Just the cost of testing every single game ever created for the old console would cost a fortune, and if just one popular old game had bugs the press and social media world would explode with hatred and attack language over the "absolute failure of the manufacturer to handle the most basic concept of backwards compatibility!!!!"
No, move forward, not back. Besides, if there is a game you love to play on the old console, just keep the old console.
Also, as the basic game play of all games is pretty much stagnate, game developers can revisit old titles and update the graphics to run on new consoles while maintaining the great gaming experience you had on the old system. It's a little like double dipping, but they can add graphics or sound enhancements to make the old game like new. That's a bonus for true fans.