[Boromir88]

…evidently not much. If he didn’t know that he would have been utterly destroyed by the destruction of the Ring, I don’t think we can place ultimate reliance upon his supposed knowledge of who could or could not use the Ring to challenge him.

I think Mansun brings up some good points...

In Tolkien's letter to Milton Waldman, he makes clear that the Ring could be used against Sauron:

While he wore it, his power on earth was actually enhanced. But even if he did not wear it, that power existed and was in 'rapport' with himself: he was not 'diminished.' Unless some other seized it and became possessed of it. If that happened, the new possessor could (if sufficiently strong and heroic by nature) challenge Sauron, 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.

And it's obvious he feared this, instead of somebody being sent to Mordor to destroy the Ring:

This was the essential weakness he had introduced into his situation in his effor (largely unsuccessful) to enslave the Elves, and in his desire to establish a control over the minds and wills of his servants.

I do agree that there is a difference between 'mastering' the ring' and 'wielding' it. To master the Ring, would be to break the allegiance and tie between Sauron and the Ring. It would break the 'rapport' and Sauron would most of his power and be diminished to a spirit incapable of reforming again. Then Lalwende brings up a good point also, can one truly master the Ring? Because even if you get rid of Sauron for good, Sauron's work will continue, as the person who mastered the Ring will in time become another Dark Lord. So, the Ring can be mastered in the sense that Sauron is no longer the ring's 'Master' but the Ring has a new 'master' a new person (say Gandalf for instance) will be the new 'Lord of the Rings.' But it can't be mastered in the sense that nothing good can come from it. The Ring will be the 'master' in the end.

To wield the Ring, would be to just carry it and use it against Sauron. I think wielding goes more along the lines of using the Ring and gathering a large army to go and overthrow Sauron. This is what it appears Sauron feared the most, especially with Aragorn being Isildur's heir. He feared that Aragorn had the Ring and was coming with an army to overthrow him. This is also what Boromir and Sam had envisioned, 'armies would flock to their banner's' and especially Boromir it would give him the power to 'Command.' Sauron was defeated when he had the Ring, so I don't see why he couldn't be defeated without it, in the hands of someone else. But, to 'wield' the Ring wouldn't be the same as 'mastering' the Ring. I don't think 'wielding' the Ring would be breaking that bond between the Ring and Sauron. You are just using it as a weapon against him, not in fact mastering it's powers. So, to use the Ring against Sauron in this manner, Sauron would be able to return, as the Ring's powers would still exist and be tied to Sauron.