I'm surprised by this article. Applematters normally provides a insightful commentary about relevant Apple matters. I don't know how 'what-if' theories of half-hearted, clueless developers running serious software companies made it onto this site.
Apple have stated publicly they are about offering the best solution, not just components of it. The iPod is an example - although they searched, an MP3 player meeting their vision didn't exist, so they made one. They apparently started down the same path with a video camera with the same intention, and found they couldn't better competitions' offering, so it hasn't yet seen the light of day. Consider software aquisitions in this context.
With this vision, it makes complete sense for Apple to aquire existing technology where it can, to save re-inventing the wheel. I can think of no aquisition that isn't quite clearly to this end (even buying a controlling chunk of Emagic was a deal to get a serious Audio app onto OSX quickly). In addition, Apple's software aquisitions have undergone significant (re)development to integrate into the solution Apple is striving for, but likwise, it doesn't fix what ain't broke.
The idea that Adobe and others might "retaliate" by ceasing development of their Mac apps is nonsensical. It is naive to think that any developer isn't striving for the biggest slice of any market that is fiscally viable to develop for. At worst, Adobe's market is 60/40 against Mac, but that is still a real 40%. Find me a developer that would willingly slice 40% or more from their established customer base because of sour grapes.
Microsoft is potentially different because a) its size allows it to absorb short-medium term impacts of willingly killing off a portion of its customer base (which is a much smaller % than that of say, Adobe) and b) because they possibly stand to actually gain something in the longer term from the Mac's demise. For Adobe and others, there is no real gain, other than to avenge "irritation".
And now with the advent of Keynote and the upcoming TextEdit /MSWord read-write features, I see the one possibly concerning hypothetical stated here of little concern also. Titles like Lotus Notes, MS Project, AutoCAD and a multitude of top-selling games are equally worthy targets for our angst, but the Mac platform has somehow survived without them thus far.
While laely Apple stands apart for its success though inovation during times where all other success from the tech sector comes from consolidation (Dell), I find it hard to believe I read this article on a site where presumably the author knows a thing or two about Apple.
Is Apple Going to iApp Itself Into Irrelevancy?