[denethorthefirst]

Of course, Sauron wants the Ring back no matter what (even if only for Safety Reasons).
IF anybody mastered it, the effect on Sauron would be the same as if it was destroyed: he would become disconnected from his power in the Ring and be reduced to a powerless spirit. But that may have been only a hypothetical threat and if anybody could really master the Ring and supplant Sauron is another Question. Tolkien himself wrote in a Letter that only Gandalf might be expected to master it, but if he really could is debatable (i think not). There is also a difference between wielding and mastering: a sufficiently powerful Ainu (for example Saruman) or Elda (for example Galadriel) might be capable of wielding the Ring and use it to dominate others, raise Armies etc. but they could not master it and would certainly lose in the final confrontation against Sauron.