Damn, I wrote a lengthy reply in the other poll-thread, which after seeing this one, is relevant to both, if not more to this one.
As I said in my other post - I feel "legacy" is changing. Legacy now days is talking about games that were programmed for sub HD resolutions. They don't translate well to most big screens we have in our homes today. I honestly believe 1080p will take us a long way, just as 720p is adequately sufficient for 5 inch screens on smartphone. Sure you can up the pixel count, but as long as the screen size stays the same, the benefit will be hardly noticable. I use a 1080p projector to project a 3m screen in my home which is pretty damn sharp. Sure 4K will be nice(r), but the benefit jump won't be as big.
In other words - the games we play today that will be "legacy" in 10 years from now, will still be a lot more compeling to play because the screen sizes won't increase much and the games of today in 720p or 1080p will look a lot less outdated then when we boot up 10 year old games today that were programmed for sub SD resolutions.