NavList:

I agree with Francis.  The first group of celestial navigators will be people who find that it feeds their soul and their creativity to do sextant navigation.  They will be around forever.

The second group will be made up of prudent small boat offshore sailors.  They know that contaminants in their diesel can make it impossible to recharge their main batteries, taking their built in instruments down...and that a lightening strike on the mast could potentially EMP all the microchips on board...including any hand-held GPSes that are not protected by Faraday cages.  They maintain their sextant skills because they want to be sure of getting home.  This group will be maintaining their celestial skills for a long, long time...possibly forever.

The third group appears to be the Navy, that is aware that any serious conflict will likely lead to them having to function in GPS-deprived environments.  Quartermasters may feel it is an exercise in futility to take regular sextant sights, since their GPS systems have never failed, and their work never seems to have any practical application on board.  But the powers that be require quartermasters to retain their skills against the day when SOMEbody on the vessel may need celestial nav.  Hard to say how long this group will continue with celestial. Depends on the other sorts of technology that may develop.

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Over against these three groups is the enormous mass of merchant mariners, who have gone "all in" on GPS systems.  They may or may not have a sextant in a cupboard on the bridge, but likely there is nobody on board who knows how to use it.  One NavLister, I cannot recall who, told a story of the first officer on a cruise ship who clearly had never held set of sight reduction tables ever before.

Along with the merchant mariners will be a significant percentage of the recreational offshore sailors...those who are NOT particularly prudent sailors.  Though it may be an urban myth (a nautical myth?), I have heard it said by Sail Canada instructors that 40 to 50 offshore yachts a year go missing.  Presumably some of these get run down by large ships.  Some get pooped by rogue waves and immediately sink. 

And some have a catastrophic failure of their electrical systems, and don't have any hand held GPS units as backups (or the hand helds that they DO have have corroded batteries).  They run out of water and die before they strike land.

Since this latter category doesn't live to write any books or articles, we simply don't know how many of them die because of catastrophic navigational failures.

And even if they do get back to land, nobody is much inclined to write a book entitled, "I was trying to get home to Seattle but ended up in San Francisco by mistake, and now my wife says I am an ass, and that she will never sail with me again."

Bob