Remember when some were saying that Gaban was irrelevant and that he would never be important or appear in the story.
And that Shiki would be the one to appear because he is more important.
Well it turns out that Shiki is the true irrelevant one.
At this point I don't think Shiki will appear or have any major role in the main story now with the exception of a Rocks flashback.
There was a reason why Oda made him appear in a movie and not in the current main story.