Typically movies with ridiculously huge first days (Friday) have quite a drop off on Saturday.  The top three for opening weekends are Harry Potter and the Deathly Hallows Part 2 ($169m), The Dark Knight ($158m) and, surprisingly, The Hunger Games ($152m).  Each of these had 2nd day (Saturday) drop offs that were at least $17m.  That one was for The Hunger Games, and what's important to note is that it is the only one of the top 3 that was released when kids were still in school.  If kids are still in school but may form a large portion of the audience during the opening weekend of a big release, then the Saturday dropoff is likely to be lower if the release is during the school year.

So, basically what I'm getting at is that it's possible that The Avengers won't have as large of a Saturday dropoff as HPatDHp2 and TDK due to those being pure summer releases.  Not to mention word of mouth is powerfully great for Avengers.  So it's definitely a possibility that it ends up having the largest opening weekend in box office history and taking that crown from Mr. Potter's accomplishment from last year, but $400m is likely asking a bit much.

Source:  http://boxofficemojo.com/alltime/weekends/

Note:  Higher ticket prices and wider releases will likely always cause these records to skew to more recent releases, so if we applied inflation and comparable screens, I'd imagine these records would look quite different ...

Sooo looking like a 68m - 70m Saturday.

That's astounding guys.,..200m OW is in play!

As is 500m Domestic Gross.

It's pretty much locked the fact that The Avengers will have a better saturday than either DH2 and TDK,since it has the highest grossing friday ever,not including midnight grosses. But will it have a better Sunday than TDK?

You're out of your damn mind.If The Avengers gets $500M in the NA,I'm gonna suck my own dick.

That´s not impossible, I mean the averngers getting 500 mil, sucking your own dick is. The Avengers movie is fantastic with a broad fanbase, earned good critics and some who have allready seen it may watch it again. And the mouth propaganda will do it´s part. And the Avengers have an advantage there is not so much worthy competition in the cinemas right now.

In the coming weeks there will be more then enough worthy competition.  The Dark Knight Rises has a much better change at making over $500 milion domestically.  It has a better track record The Dark Knight did it and it being released on July 20th relatively late in the summer movie season it faces a lot less worthy competition in the weeks after its release.

I'm going to try to watch this movie tommorow.

If OW is 200m than a 2.5 multiplier is not out of the question given the word of mouth which according to many on BOM is TDK level in America.

NONSENSE. I don't want to hear such nonsense anymore!