The ring is cursed. After Liam gives the ring to Charlie, Charlie develops a self destructive drug habit. Liam on the other hand gets married, has a kid, and gets sober - everything he predicted for Charlie. Perhaps, by leaving the ring behind, Charlie has broken his death curse.
This ring could bring curse upon itself,cause it seems like before recieving this ring his life was so happy,but after that he loses everything and his brother gets a better life instead.now the ring is left on the island and it can be another reason for the plane crash and Charlie's death.
The ring will eventually be used by Sun as a token of remembrance (or a constant) to convince Claire away from the possibly evil Christian Shephard.
Sun will find Claire with Christian and show Claire the ring and breaks whatever trance Christian has on her and will ask where Aaron is. Sun will say off the Island and Clarie would try to Aaron and some how she couldn't and gave the ring back to Sun and tell her to give it to Aaron and would say something like It would be what he would want.
Or the ring would be like the rin on Lord of the Rings which Dominic played the role Merry in.
The ring is in a time loop. It will eventually be given to Dexter Stratton.
Everything in a time loop (the numbers, the compass, the ring and John Locke) is cursed with bad luck.
I like the idea of it being given to the original owner. Hadn't thought of that. I was thinking though, even if WHH is wrong, the ring being there in 2007 DOES HAPPEN, even if Jack and co did change whatever happened between 1977 and 2004. So 815 may not crash, but somehow the ring gets put exactly in Aarons crib (assuming its still aarons crib) at the losties beach camp (assuming its still the losties beach camp)