It would be great if the Harp was somehow connected to Sheik's from Ocarina of Time. This is one of those trivial things Nintendo should capitalize on. Seriously, if fans were to find out Skyward Sword's Harp is connected with OoT's or it's the same one, many of them would have a heart attack (including me); it's just seems so significant. This would exude a "wow factor" that would stick with us fans forever; it would be the same if any other popular speculation was confirmed!
It would also (kinda) indirectly give Sheik a little backstory, 'ya know (yes, I know, Sheik is Zelda).