[the phantom]

Its strenght, Boromir, is too great for anyone to wield at will, save only those who have already a great power of their own.

Yes, that is true. In other words, it takes someone with great power to harness the power of the ring and with it do their will. But that doesn't mean they can do it forever. Soon, the will of the ring will taint them.

and the one on the Dark throne didn't win either for it was not his intention to become Dark Lord

Exactly what I'm talking about. The ring will taint them.

It's the Ring that will win in the End if someone should stand up.

Precisely. The ring would be master in the end. Sauron wins.

The first is that the Dark Lord could be overthrown if someone else with a great power of his own should take the Ring and wield it.

Yes, I already said that. He would be overthrown in the sense that his armies are wiped out and he possibly has been physically destroyed. But again, it wouldn't last. Sauron is not defeated forever, because the ring is still there, on the hand of the new ruler.

the phantom - you said that Sauron was not afraid of being overthrown, but of delay

In this sense, I was referring to "overthrow" as complete defeat, the ending or near ending of his spirit. He was afraid of being overthrown militarily, a temporary overthrow (a delay).

Yet the fact that the Ring would corrupt the heart and mind of the one wielding it at that time, is another thing. That would not help Sauron.

Sure it would. If a wielder is becoming more corrupt, that means they are succumbing to the ring more and more. That definitely helps Sauron.

The second is that he says that he (Elrond) won't take it to wield it, meaning that he was indeed strong enough to wield it. Galadriel's quote when she gets the Ring offered freely from Frodo fits into this as well.

Why don't you check out this quote from JRRT's letter 246-

It was part of the essential deceit of the Ring to fill minds with imaginations of supreme power. But this the Great had well considered and had rejected, as is seen in Elrond's words at the Council. Galadriel's rejection of the temptation was founded upon previous thought and resolve.

It had to be founded upon previous thought and resolve because she wasn't thinking clearly once the ring was within her grasp. As Tolkien clearly states, it IS the ring's intention to tempt with power. So I ask again, would the ring do something that would bring complete destruction to its master? I think not.

I'm going to quote you again-

It's the Ring that will win in the End

That is completely true. If it was not destroyed, the ring would've won no matter what course of action was taken.

And Sauron remains as long as the ring lasts, and he's the Lord of the Ring. The power and will of the ring is his.

If the ring endures, it wins. If the ring wins, Sauron wins. Do you get where I'm coming from?