Manchester United coach Eric Harrison said Beckham will need six weeks to recover and not eight as originally feared.
The prediction was made after it emerged he had broken his second metatarsal bone and not his first.
If all goes well Beckham could still play a part in England's final friendly against Cameroon on 26 May and be ready for the opening game against Sweden on 2 June.
But the severity of the problem will not become clear until the plaster cast is removed, with the possibility of complications or recurrence.
'Difficult to heal'
The second metatarsal bone is one of five long tubular bones found in the in-step.
The bone is in a fleshy, relatively protected part of the foot, and is not often broken.
In the case of a severe break surgeons would have considered operating, perhaps inserting screws and bits of metal to stabilise it.
Professor Tom Reilly, of the Institute for Sport and Exercise Sciences at John Moores University, said: "The first metatarsal would probably be more difficult to heal because players do most of their kicking with that one.
"The second metatarsal would be bad news for a runner and it is involved in weight bearing."
He agreed the break would take around six weeks to heal, helped by Beckham's high fitness levels.
Muscles 'weakened'
Dr Mike Smith told the BBC another danger was breaks to Beckham's pre-World Cup training regime.
He said: "He won't be able to train so therefore he has got to get fit again.
"His muscles are going to get weak and they're going to become thinner than they were before and that's got to be got back under training.
"So it's unlikely he will be able to play for something like eight weeks with luck."
He said it was likely to be the way Beckham landed that caused the damage.
He said: "The chances are it would have bent it down as if the toes were going down so pulling the bone and fracturing it that way."
Asked whether he thought Beckham would play in the World Cup, he said: "I wouldn't put money on it."
Painful healing process
However, medical opinion differs and orthopaedic surgeon Michael Sullivan thinks there is a slim chance he could make the World Cup team.
Speaking on BBC Radio 4's Today programme, he said: "Yes, I think he would be able to play.
"But he won't have played for some weeks before, which has its own problems."
He compared Beckham's injury to the type of accidents boxers endure.
He said: "It's like the one that boxers break in the hand, which is the metacarpal.
"Boxers break them when they hit people and footballers break the metatarsal when they kick something."
Exercise regime
Essex county cricket club physiotherapist James Davis said Beckham can maintain his physical fitness over the next few weeks with a regime of non-weight bearing exercises.
He said: "Nothing will accelerate the healing process, but it's important he keeps the rest of his body fit.
"He could do sit-ups and press-ups and could run in the pool, which would keep up his cardiovascular (CV) fitness."
Another activity, to maintain his CV fitness, would involve cycling in an oxygen chamber using his good leg, to mimic training at an altitude of 9,000 feet.
Mr Davis, who runs the Anglia Spinal and Sports Physiotherapy Centres, also recommends exercises like hamstring curls and quad bench work to maintain leg muscle tone.