Paul (and others),
The thing is that this fear is in large part based on the assumption that 3rd party support would eventually cease just because of certain assumptions about what's going on now.
I would submit that's a very unlikely scenario unless the camera makers actually go to the extreme of properly using strong encryption to lock out 3rd parties *AND* effectively throw away the "key" themselves (by ceasing support themselves for whatever reason).
If there is actual $$$ to be made, somebody will more than likely pick up the slack. If there is no $$$ to be made, then no amount of letter writing will help. Now, I don't mean it has to be $$$ made directly from offering support, but could be indirect also. For instance, if Nikon went to the feared extreme and then ceases support for a lot of iterations of their NEF format while other makers do not do that, then Nikon will lose marketshare due to customers losing faith, which means $$$ lost.
We should recognize that much of what's happening right now is probably more about posturing between the Adobe and Nikon than Nikon necessarily heading toward that feared end. Even if Nikon decides to go the extreme route tomorrow for all future bodies, your current existing NEFs will still have 3rd party support and will still be accessible w/ today's Nikon software. Just don't buy Nikon anymore if it comes to that. You know the "funny" thing is that all this is coming back to bite all the Canon shooters who want a new model every 6 months because now Canon can't keep up w/ support -- today, it's D30, tomorrow 10D/20D/etc.
Of course, 3rd party support might not last forever if the costs involved are too great, but then again, if the costs are too great, then it probably means not enough people are willing to pay enough for the support. That would probably be the same underlying reason why a camera maker might cease support itself.
Sure, let
all the camera makers, not just Nikon, know your fears, even if you only own Nikon gear -- afterall, you're a potential customer for non-Nikon gear. But I'd submit that most of the fears are a bit overblown and not accounting for market realities.
Also, if it really comes to that, it's a virtual impossibility for your RAW files to become so obsolete so fast that you have no opportunities to convert them to some other high fidelity format anymore, eg. 16-bit TIFF as you pointed out or maybe Adobe's DNG (ack!

). The only threat here regarding existing RAW files, and a somewhat remote one at that, involves
future advancements of RAW conversion of your existing RAW files, not so much whether you can still convert them at all. Again, if and when support ceases permanently, just do a final conversion w/ the best latest available software. At least your RAW files and whatever other final format you choose are digital and won't wear away from errosion over time like film does.
RE: the example of word processing documents and such. I assume most of those cases either involved small companies w/ relative small customer base or are simply niche markets. Otherwise, somebody would be persuaded to make $$$ by offering support of some sort. Consider the computer programming field itself. Who's really writing new code in Cobol now? But you can bet there's still $$$ to be made just for the maintenance as long as the legacy stuff are still needed. If you know Cobol, go get that $$$ -- maybe I should go for that when I'm too old to keep up w/ the field.

If you don't know Cobol, you can learn it.
Finally, I think we have to remember that these are all business entities w/ $$$ as their bottomlines (for the most part). If we believe there's a problem and want to be proactive to help solve it, we need to give proper consideration to the big picture for all involved, not just for our own fears of obsoleted photographs or whatever inconveniences or lack of choices. It does little good to merely yell at somebody to simply "do better" afterall.
_Man_