It's possible. The eye strain is real after a couple hours, though. And I've already run into situations where I wanted to show someone something and had to "change modes". Having the laptop display for auxiliary use still seems important, although you could probably get away with crappier and cheaper screens again.
I hope at least Samsung Dex/Android Desktop has a natural way to plug-in-play into these things, maybe that'll force the iPhone to offer a handheld desktop mode.