Could Númenor Have Been Redeemed?
 

The Fall of Númenor, I think, had its roots in two things: the nearness of the land itself to the Undying Lands in the West, giving the Edain who dwelt there a constant reminder that they had not the life of the Eldar; and the very bliss of the Númenóreans' lives: the more joy they had, the more they wanted.
Now Sauron, when threatened by them in his goal to conquer Middle-earth, determined that he could not defeat them militarily. His best hope was to get near Ar-Pharazôn, the King, and exercise his guile and superior will. He managed to do so, eventually ruling Númenor in all but name.
Númenor was destroyed, as we know, when the Númenóreans were influenced by Sauron to attack Valinor in a vain attempt to wrest immortality away from the Valar.
The seeds of its destruction were already well in place before Sauron set foot on the isle. However, it needed his evil deceits and control of the King to set into motion the events that led to the Downfall.
The question is, could the Dúnedain have found wisdom again, and backed away from their perilous course, if they had not brought Sauron to the island? Tar-Palantir, Pharazôn's predecessor, tried to turn things around on his own. Were there enough of the Faithful left on the island to have brought about change? Amandil, father of Elendil, was said to be a close friend of Ar-Pharazôn even though they were of different minds regarding the Elves. Without Sauron, could things have ultimately turned out differently for Númenor?

Interesting question i don't believe they would have attacked Valinor without Sauron's influence. That said i believe the Numenoreans were becoming lesser men because of growing hatred for the Valar and Eldar. Perhaps if there lifespan diminished further they would have rediscovered there faith or maybe this would have expanded their hatred hard to say good question. I have to think about it more and write back. Thanks

It seems to be fairly clear that the bulk of the Numenoreans
were too far gone to reverse their fate. Consider that Tar-Palantir's
efforts failed and that a far more sustained effort, and more committment
by the bulk of the Numenoreans would have been required.

But without Sauron egging on the great majority of the Numenoreans
there would probably have been a slow decline in their "happiness"
and drive toward imperial rule in Middle-earth, which paradoxically could
have led the faithful to slip away from Numenor to northwestern Middle-
earth, setting up a complex geopolitical situation of strong realms of
the Faithful, strong southern enclaves of Numenorean colonies interacting with nativist peoples and elves inland and with Sauron and his lads hovering around.
Numenorean physical and mental decline should eventually sap the strength
of the home island leading to independence movements in their colonies.
(T.A. 1776 :D )

Which I imagine would bother Sauron less then a Numenorean 2nd invasion
aimed at him around T.A. 1066.

Depends on what you mean by wisdom. The Numenoreans, being Men, would eventually have sailed to Valinor regardless of Sauron's influence. Maybe not with the explicit intent of making war but still. The Valar really showed how little they understood Men by taking them within reach of Paradise saying: "you should be happy with what you've got!"

Would they? It took Sauron lying personally to an old King who feared death to set them on their way. And even after all Sauron's efforts, Pharazôn was that close to calling it all off when he came in sight of Valinor.
Had Sauron not been taken to Númenor, I think they would have continued on as conquerers of Middle-earth, despots ruling over the Men there. After all, that was Pharazôn's motivation for going to war with Sauron in the first place- to challange his supremacy in Middle-earth. If he had been content with Sauron's defeat, and perhaps established a kingdom there, I think it possible that prolonged contact with 'lesser' mortal Men might have given his successors pause. Maybe if their interests had been more established in the East, they would have turned their backs on the West. I'm not saying that what they created would have been as noble as what the Faithful did with Arnor and Gondor, but surely it would still have been better for them than making war on the Valar.

Call me a fatalist, but my answer to the question is pretty succint: no.

FATE plays a huge role in the history of Middle Earth. Numenor was fated to fall. For one thing, nothing pure and good can last forever in a world with evil. Not even the Undying Lands. As the music of the Ainur played out, the dischordant notes only added to the beauty of the whole composition. The Fall of Numenor allowed for great deeds of honor and valor to be possible, for the redemption of the Dunedain beyond hope, the rise of hobbits, and many other great happenings ad nauseum.

For another thing, men are men, even the Dunedain. Their hearts are easily turned to evil, and as a race cannot wholly withstand it forever. I think that is partially why Death is gifted to the race of men. Eternal life like that of the Elves just wouldn't work out well for someone who's bound to go bad after a while. Better to die young and innocent. ;)