Long time lurker, thought I'd just weigh in after the results of this past weekend. Overall, Endgame is definitely going to pass Avatar, though it will take longer than most expected given the monstrous worldwide opening weekend numbers.
It left it in pretty good shape for the 11th weekend, now merely $15,513,852 away from the goal, and it just had a 4.4 million dollar worldwide weekend with pending countries slated to open for re-release throughout July. Plus the run still has more than two months to go, over Labor Day and into September.
Domestically speaking, weekday and weekend declines will be like 50%, and knowing what Endgame made last week ($2,872,936 weekdays, $3,100,000 estimate) we'll likely see about 3.5 million for all of next week. Then about 2 the whole following week, then 1, then 0.5 at the end of the month, going into August. The entire month of August will give at least another million (which is what Infinity War did) and maybe a bit more in September, too.
So altogether domestic has about 8 million left in the tank, taking us to 856 domestic (from current 847.8) and the remaining total down to 7.5 million, which has to come from overseas.
International is tricky but 7.5 million is quite doable with them having them expanding in different countries on different weeks. Worldwide, excluding domestic, they will make about 1-2 million each entire week of July, plus whatever they get in August, probably less than a million for the whole month. When all's said and done it appears that it'll come to at least 1932. Enough with domestic for it to just barely take the record, probably sometime in August.
It's so close now, it's gonna happen eventually. If it doesn't surprise in July or get it in August and September, I'm betting they will keep it in theatres even into October to trickle things past the finish line, like what happened with Black Panther in reaching that 700 million domestic milestone.