I didn't think there was really anything to this except that Hurley would be a proxy for Charlie. Like Locke with Christian's shoes, Sayid in handcuffs (Kate) or Sun with the wedding ring (Rose), Hurley bringing a guitar helped to recreate the conditions of flight 815. If that's the case (no pun intended!) it's probably just a guitar. The real question is, can Hurley play "You All Everybody"???
I had the same kind of thought, that Hurley would somehow leave the case for Charlie - assuming of course, that it's a guitar. Darlton better not just be screwing with me, getting my hopes up that I'll see Charlie again.
I definitely think that the case, guitar inside or not, is significant, and we'll see it again.
Well Jacob left it there for Hurley for some reason. And Hurley was the only one Jacob talked to about the island and asked him to come back. And he made a point of telling Hurley he wasn't crazy but blessed. I still say Hurley is the key to all this.
There is something about a musical instrument in a case. The shipwrecked Frenchies had a violin, 815 had Charlie's guitar in a case, and 316 had Jacob's guitar/case carried by Hurley - assuming that what's inside the case Jacob left for Hurley is a guitar.