At the time of the Athrabeth commentary, which postdates virtually all Tolkien's narrative writing on the First Age
, T felt so strongly that the End was *not* prophesied in any specific sense that he repeated himself:
The Elvish conception of the End was in fact catastrophic. They did not think that Arda (or at any rate Imbar) would just run down into lifeless inanition. But this conception was not embodied by them in any myth or legend.
and again, as given upthread by scirocco
The Elves expected the End of Arda to be catastrophic. They thought that it would be brought about by the dissolution of the structure of Imbar at least, if not of the whole system. The End of Arda is not, of course, the same thing as the end of Eä. About this they held that nothing could be known, except that Eä was ultimately finite. It is noteworthy that the Elves had no myths or legends dealing with the end of the world.
These two passages reflect Tolkien's last statements on the matter. I don't see how in that light the Second Prophecy could have survived (except of course for Arda Healed, but *only* that small part, which really is an independent concept). The rest of it had become as superseded as the idea that Túrin and Nienor would be joined to "the children of the gods."
There is also the problem (fatal, to my mind) that the 2PM, which was never really modified from its 1930 form, takes no account of the Catastrophe of the end of the Second Age; it assumes a word still flat at the End.
There is the "Mannish tradition" dodge. But that's an alternative 'framing device' which Tolkien really never even began to work out. It's clearly not the same as the Eriol/Aelfwine story, since that always assumed a direct relation of the lore of Eressëa to a Man of historical times. Nor can it be squared with the "Bilbo frame," since Mr Baggins also learned directly from the Elves (and perhaps Gandalf).
I'm sorry, but if the guideline is "Tolkien's final intent (consistent with coherence)", then the 2PM is gone, obsolete as Tevildo Prince of Cats.
While it can be objected that the old tale of the Sun and Moon also was dispensed with I would agree but refer again to "consistent with coherence:" the overhaul of the astronomical myth was never undertaken, there was no replacement for the old version; and the overhaul would have wiped out the idea of Eärendil's Silmaril as the Evening Star among other brutal wounds.