User blog comment:Haki73/Blackbeard's Strength/@comment-220.255.7.164-20100815102450

Luffy already have Soru, in Gear 2nd. He moves just as fast. What I'm guessing is that Chopper might make new medicine to control Luffy's downsides eg. (Life shortening for gear 2nd, chibi mode in gear 3rd) And he'll invent gear 4th and haki together.