Initial indications pointed to a six-month recovery period, ruling Mitchell out of the global gathering in New Zealand in September and October.
But the 27-year-old Wallaby regular has today stated that his World Cup dream is still very much alive after he presented a different take on the length of the rehabilitation process.
"The indication I got is 12-14 weeks," Mitchell told the Sydney Morning Herald.
"It is much better news than it could have been. I was immediately trying to work out how many weeks it would be before I could possibly return.
"It has put me in a better place than what it could have.2
And Mitchell, who is approaching the 50-cap mark, insists that the presence of the World Cup will only quicken his return to action.
With Australia having reached successive World Cup finals in 1999 and 2003, Mitchell's first World Cup ended in disappointment when the Wallabies were knocked out by England in the last eight in 2007.
"If I had been looking at the World Cup as not being an option at all, sometimes the motivation might not have been as high as it could be," added Mitchell.
"I'll make sure that whatever day-to-day rehab stuff is required, I will do.
"It will be tedious and boring but, if that tedious and boring work is going to put me in a position to hopefully be looked at for World Cup selection, it will be worth it.
"Also, ever since the last World Cup when we were eliminated in the quarter-finals, from that moment I have done everything I can to get back for the next World Cup."