This is already happening. We have devices in the market that already have high pixel density displays besides Apple's Retina screens and we know no one plans on scaling back on this technology. We also know that, all though, the majority of these devices are on mobile phones and tablets, mobile is playing a larger part in the web and also isn't going to start slowing down any time soon.
Will we all just blindly follow Apple's iOS workflow and create multiple assets for multiple resolution targets? some-image.png and some-image@2x.png?
There's definitely more options than this and the web isn't such a simple place where we can just accept apple's native app work flow and expect it to work without any consequences.