I think people who need to manage files outside of a particular application will become the exception, not the rule. As long as you can access the underlying file system when you need to, I see no problem with most people not having to care about it.
How do you move photos from Alice's computer to Bob's computer? "Check out these"? With the concept of files, you can move photos/music/whatever in a number of ways - thumb drive, network shares, cloud. If you only work through 'photo manager' applications, how do you do it? What if the creators of the photo manager didn't want to support thumb drives? What if the way the photo managers on the different devices use different ways of referring to the photos?
I think 'regular' users have plenty of use for understanding the filesystem. I also think that it's okay to have some degree of expectation for the user - dumbing it down for the lowest common denominator is harmful (look at politics!). What do you really gain by alienating the power users?
You're still thinking of exceptional cases. Photo managing applications have, and will improve, native ways of sharing the photos, even if it's as simple as sending an email.
I see no reason why making the common case simple (not "dumb") means you have to eliminate, or even alienate, the power users. Frankly, since I started using a Mac, iTunes and an iPhone, I stopped managing music files. And I think that's great. Files are an implementation detail. What I want is music or radio programs, not files.
It's an error to simply transfer "it works for music" to "it works for everything". That it works for music is largely because sharing media files is verboten in our Brave New World - sharing is not a problem that needs to be solved there. But sharing non-media files between users is not an exceptional case, not even remotely - it's common as muck in business.
The idea that the 'normal' user is only a home-based casual web-browser/photo-taker/music listener is misleading from the outset.
