Yep. Hell, I can pretty much sense their return at the end of the series.
Luffy finally achieves One Piece. Shanks and his friends remind him that his journey has just begun. Suddenly, all the villians that the Mugiwara's have ever fought appear over the horizon. They have conjured a combined force to take them down.
The heroic moving music plays.
Usopp redies his slingshot.
Nami smiles and grabs her Clima Tact.
Zoro puts a sword in his mouth.
The rest of the crew member's do the same.
Luffy charges towards them while the music reaches it's climax. Luffy and his crew jump towards the army of villians symbolizing they will never give up the fight, and at that moment, BAM, fade out, or a possible freeze frame, then the frame switches to colored penciled art, and then fades out.
End of series.