A devil fruit is the only way those two would even be able to challenge Luffy. There's no way those two punks would get strong enough on their own.
It's funny how they think (watching 463) that they can become Admirals as long as they don't die. Aren't Admirals supposed to be incredibly strong?
But to be fair, they'd die instantly if they tried to take on any Whitebeard Pirates. Maybe if they luckily wound up fighting one of the weaker ones but meh...
Lol... Well talking about 2 years skip.. Then the adventure when Luffy finaly becomes pirate king.. In the One Piece world.. That will take 1-2 years as well?
So let us say... 4-5 years.. Coby and Helmeppo can be strong... With the proper use of Haki and stamina build..
As for Coby.. I'm not sure if Oda would ever give him a devil fruit.. I just think he wouldn't.. About Helmeppo.. Not sure.. His dad was "
strong".. But if any of those 2 would get.. Think it's Helmeppo tho..
I think that Coby will be more like Garp. He's getting trained by him as well.
Meh, thinking and speculating about this stuff.... Makes me want to skip time by 5 years and watch/read it all at once. xD