Tighter controls around dog ownership and dog breeding.
As it stands, anyone with a dog can breed from them and sell them to total strangers on the internet. There's nobody policing it, nobody making sure the dogs are healthy or of sound temperament. Nobody making sure the new owners have the time, money or knowledge to raise a dog. Nobody to make sure the dog will ever see a vet or attend any kind of training class.
Until the dog breeding laws are tightened, dog attacks will just continue to rise. The XL Bully might get banned but another breed will come along and take their place (after all, that's what happened when the Pitbull got banned).
As PP have said, the current BSL legislation only applies in public. So these dogs will still be kept, unmuzzled, in people's homes - and what happened to Ian Price will continue to happen, because any dog can escape out of a door or through an open gate.