Actually, I expect the Mac itself to evolve in this same closed direction over the coming years. To avoid a potential torrent of complaints, Apple may retain optional access to some areas, but they will be inaccessible by default (similar to how the home directory Library folders in today's OS X are hidden by default). I can even imagine a setup where under-the-hood OS access is limited to Apple developers, consultants, and technicians.
I believe Apple when they say that they have no plans to merge iOS and OS X. However, it still makes sense for OS X to adopt more and more characteristics of iOS over time. Macs were once called "personal computers," but that's a 20th-century designation that's rapidly vanishing. In the 21st century, Macs are becoming yet another "digital device" — closer to the simplicity of iPads than to the Macs of old. Tomorrow's devices will push that envelope even further.
This is the direction that all digital devices are headed. We are approaching the day when the need for end users to fiddle with the likes of Library folders will be as rare as the need to re-solder a logic board is today. As this future gets closer, traditional troubleshooting will increasingly become something we spy only through our rear view mirrors.
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