I think they are probably the same, but I would rather like to think that they are different skull kids. After all, in Ocarina of time we saw three different ones, the one who you give a mask to, and the two that you play songs with as a young child to get a piece of heart. Their personalities are a bit different, so I think that they are different ones, though they could very well be the same since as far as I know skull kids don't die (or at least live a very long time).
I would very much like to see skull kid again, he is an interesting character with much unknown parts to him. I liked him and I think the character has a lot of potential.
Whether or not Nintendo will put the skull kid in another game is unsure. Somehow I feel that they would not have him in another game. Though I would wish that they would do so.
All in all, a great character and would love to see him again.
