I've been following the BO of Avengers and have seen some interesting things. 

DBO

First for the "bad."  While IW just had the largest DBO opening ever, it's become very clear that it will not be taking the #1 spot from SW:TFA, which sits pretty at $936.66M.  IW did start out ~$10M ahead of it after opening weekend, but can't compete with the weekday numbers and has fallen $70.42M behind it in just 5 days.  On the plus side, it will become the #1 superhero movie of all time, taking both that title and #3 from the Black Panther. It is currently outperforming BP by 15.3%.  BP will finish its DBO run with ~$700M, so if IW's performance continues it will end with ~$807M.  This would also give it the #2 spot on all time DBO takes.

FBO

This is where IW is trouncing TFA, at least for now.  After TFA's 2nd weekend, it was at ~$546M at the FBO.  As of this Fri, IW was at ~$604.8M, a difference of ~$59M.  And it has two more days in its 2nd weekend, so the gap will more than make up for the DBO gap.  China will also make a big difference.  While TFA did a respectable $124.16M, IW should, at the very least, come close to matching Avengers:AOU's $240.11M.  I think IW has a good shot at doing $1.3B-$1.35B, just at the FBO.

Conclusion

So, while I think it is very clear that IW will fall ~$130M-$160M below TFA's DBO, I think the FBO will more than make up for it, pushing its final WW BO to ~$2.08B-$2.16B.  This would allow it to either take #2 from Titanic or #3 from TFA in the all time WW BO.

Edit:

BO = Box Office, DBO = Domestic Box Office, FBO = Foreign Box Office 

Added a little legend at the bottom. 

Yep. 

It's already the fastest movie ever to get to 1 billion, in 11 days (12 days for TFA). And it's without China. With the very good critics and word of mouth around it, it should keep strong numbers.

I really hope it beats Star Wars: TFA but I also see it slowing down a lot from this weekend onwards. Deadpool 2 is coming out May 18th and then Solo: A Star Wars Story comes out a week later. Solo should manage at least 1 billion WW (Though I assume it will be the lowest grossing of the new star wars movies) and if the reviews and word of mouth of Deadpool 2 are as good as the original it will come close to 1 billion WW as well.

Already two movies at 1 Billion+ WW. I wonder how many we'll have by the end of the year. So far the highest was 5 back in 2015.

Personally, I doubt it will end up quite as high as people think. The whole movie one such massive spoiler fest, I'm inclined to believe everyone was just trying to see it as quickly as possible for fear having too many moments ruined for them if they decided to wait. I'd look for it to fall off quite heavily in not too long.

Not sure about Deadpool 2 though. It will surely be awesome like the first, but it's clearly not a movie for everyone like Avengers. And isn't it R rated in some countries? The first one did less than 800M, I'm even surprised by this number actually. I thought it would be lower. 

Solo will surely get the billion, but it might be low. It doesn't seem to have a lot of hype around it, and the last SW movie being very controversial won't help them to keep huge numbers for each new movie... Anyway, I'm not sure those movies will lower the result of IW. Fans of comics will see IW before going to see DP2 too later, rather than the opposite I guess.

Hey, feel free to go off of topic a little. Not going to piss me off any. And I agree, it was great. Personally, I think it's Marvel's best. 

Deadpool 2 might surprise, but I personally see it doing less than the 1st. Not much less, of course, but I think the novelty of a Deadpool movie done right has faded somewhat. As for Solo, I don't see it hitting $1B. Not after TLJ, which caused many to lose interest in the new series. There's also all the negative things that went on behind the scenes looming over its head. We'll see, though. 

It's already at $1.164B in less than two weeks, so it's still got at least 4-6 good weekends left, plus China. Where do you think it will end up? 

Looks like IW is now at $1.164B. This is $78M more than TFA was at the same point in time.

It'll end somewhere between 1.7-1.9 billion 

If it crosses the 2 billion mark will be an extremely feat. I bet on 1.8 billion at most.