Lmao dude it's gonna beat Avatar. The question is will it get to 3 billion. I don't think it will but it will be close. Passing Avatar is a foregone conclusion though so I don't know where you got your numbers.
Well, math is not really my forté but...
The movie needs $299m more to catch up with Avatar. It made $296m this last week Worldwide, which was a 70% drop from previous week.
Now, if we assume a 50% drop every week for its remaining time on theaters (and I am being REALLY generous with this drop) it would need 10 more weeks to catch up to Avatar.
So, I think it is possible for it to beat Avatar, but I'm finding that to be really (and I mean REALLY) hard. Now, like I said, math is not really my thing so if you have better projections I would love to hear it.