There's a chance... just a CHANCE... that people will fear the death of Mac because "there's no need to write Mac apps anymore."
I'm not afraid. People WILL write apps if there's anyone to buy them. Demand means income, and that's what developers seek.
And DEMAND for real Mac apps will hardly go away. Tacking Windows apps (for a price) onto a Mac is a neat option, and one that will bring new users to the platform, but it's not AS GOOD as a native Mac app with the Mac OS X benefits that brings. Nor do a lot of apps run at all.
So people won't "settle" for Windows apps on a large scale, anymore than they'd "settle" for taking OS X off of their Mac and running Windows. We use Mac OS X because it has real advantages. When you need a non OS X app, it's nice to have these options.
Any trickle of people who choose to buy Windows apps for their Mac INSTEAD of an existing Mac app will be more than offset by the increase in Mac sales overall.
The market for Mac native software will grow, not shrink. So I welcome these options.