User blog comment:DomoGanchan/Luffy will have 6 gears?!/@comment-24850639-20170213144309

I think we need to hold out on more details about Gear 4 before we can explore others. We haven't even seen probably 40% of what all he can do with it, given that there's other forms to it too. Its the first form he's combined with haki, and the fact that him being able to retain his devil fruit's original properties confounded an expert like Doflamingo says quite a lot. But then again, maybe we'll never get an actual explanation. At the very least I'd have to say that "Awakening" does open the avenue for at least one more gear probably.