Oda-sensei might be giving Luffy a haki upgrade, but even that cannot answer One Piece's most burning question that compares Luffy with Roger.

However, the world of One Piece thrives on balance. While these powers seem nearly invincible, hope lies with characters who possess extraordinary Haki mastery. As a manifestation of willpower ...

Ever since the very first chapter of One Piece, Devil Fruits and Haki were introduced as the primary power systems of the world, despite the latter only being fleshed out properly later on.