Does Al-Qaeda even have a shot at this?
Their chief and most identifiable capability is their suicide bomber, which depletes their numbers every time they use it.
ISIS gives the impression of being much better armed and organized.
Al-Qaeda was never set up to wage a conventional force on force war. While that might seem like a disadvantage against ISIS it actually plays to their favor. While ISIS is openly fighting everyone and taking sizable losses in the process, Al-Qaeda can operate in the shadows and stick knives in the backs of those who need it to either take control of the organization or destroy it.
Hell, with their network and contacts I'm pretty sure they have a wide choice of nations on speed dial who will be quite happy do a lot of their dirty work for them either wittingly or unwittingly. When the enemy of your enemy has drones and SEAL teams you don't need a big army and lots of equipment.
The real question is whether or not ISIS has the spies and informants it needs to be able to root out Al-Qaeda.