I don't see it taking over for everything necessarily, but there are a lot of places it would help. Like Paprika Recipe Manager, which costs $5 for the iPhone/iPad universal app, but if I wanted the Mac version it's $30. Part of that is a "because I can" pricing, the market will bear it because there's just not that much competition compared to iOS apps. Another part is "because I have to," it's a much smaller market and a bunch of additional work to make the Mac version, so the price has to cover those costs with fewer users.
If it didn't need a totally separate UI framework, ports like this would take less effort and more apps would do it. Maybe you can't sell it for 6x the cost any more, but a comparatively small amount of work gives you a leg up on the competition.
Twitter is another example. They killed the native Mac client earlier this year and said "For the full Twitter experience on Mac, visit Twitter on web."
If it didn't need a totally separate UI framework, ports like this would take less effort and more apps would do it. Maybe you can't sell it for 6x the cost any more, but a comparatively small amount of work gives you a leg up on the competition.
Twitter is another example. They killed the native Mac client earlier this year and said "For the full Twitter experience on Mac, visit Twitter on web."