[Boromir88]

Again, I'm just completely failing to see how that statement admits of any other possible interpretation than only Gandalf could master the One Ring.~Kuru

Sorry, if it feels like we're gaining up on you, but besides what davem said, 'expectations' are not always certainty. And that's exactly what the Letter 246 quote says...'might be expected.' Again, even if Gandalf was the only one expected to be able to master the ring:

1) Doesn't mean that he could do so.
2) Doesn't mean anyone else wouldn't be able to do so.

Like the Italy-USA example given. You're focusing on the world 'only' where the words of 'might' and 'expect' add ambiguity to the quote. 'Might' is a term of uncertainty, it 'may happen' or it 'may not happen.' And expect is another term of ambiguity. Like, I expect USA to win the Olympics, it's something I definitely think is going to happen, 'I'm expecting it,' but that doesn't mean USA is going to win the olympics. Same case in this quote, you're putting emphasis on the 'only' where might and expect is what adds ambiguity and uncertainty. Tolkien being the linguist, and on the back cover of Letters of JRR Tolkien him saying the importance he put on every single word (which he guessed was over 600,000). So, I don't think 'might' and 'expect' two words of uncertainty should simply be ignored.

I said I agreed with you (and I still do), in that Saruman did not possess the capability, nor perhaps the knowledge it took to master the Ring, I'm just pointing out the ambiguity that Formendacil and others have noticed with Letter 246. The quote is not so rock-solid and sure as you have made it out to be.

Why then did Tolkien write about Saruman coming in for the Ring, if he had no chance of wielding its powers?~Mansun

It's called pride, Saruman was prideful and confident in his abilities to fool Sauron so he could profit. Just because Saruman believed he was pulling one over Sauron, and had thought he was capable of mastering the Ring, doesn't mean he actually was. And as Grishnakh says, it was Saruman who was the one being fooled. I'll give a perfect example, Denethor and the palantir. Denethor believed he had the strength and will power necessary to challenge and beat Sauron in the palantir, but this didn't happen:

Thus pride increased in Denethor, together with despair, until he saw in all the deeds of that time only a single combat between the Lord of the White Tower, and the Lord of Barad-dur...~Appendix A: The Stewards

Denethor believed (key word being pride) he had the will it took to view the palantir and one-on-one challenge Sauron, but he was beaten and his mind was eventually overthrown.

Gandalf himself says that he IS Saruman when he re-appears. That would also suggest, I believe, that if Gandalf could master the Ring, so could Saruman.~Saruman

But he actually says that he was 'Saruman as he should have been.' So, he actually wasn't really Saruman, but he was as Saruman should have been as the head of the Order.

In addition, Saruman's ring-lore must be considered, and I would imagine that he knew more than Gandalf or any other of the Wise.

I don't think it took knowledge about the rings (and I actually think we are told Saruman's main interest were the three elven rings, but don't hold me to that ). As the quote to Milton Waldman suggests...

become master of all that he had learned or done since the making of the One Ring and so overthrow him and usurp his place.

This seems to stress the importance of actually knowing what Sauron was doing since making his Ring, more than the fact of knowing about the Rings of power.