623m is huge number and to duplicate it, it needs to be in the same ball park as TA, even sometimes in the case of SPIDERMAN movies, the sequel was better liked and it still grossed less because the target set by the first one was huge much like another small franchise called STAR WARS.
You know we could also say that the first TA was sold by the introduction and first collaboration of superheroes ever. Now that is not going to be the huge draw it was back in 2012 and it will have nothing new to offer to the GA. Introducing two unknown characters won't boost it's chances of over grossing the first one. The max I see for this is 500m.
Could very well happen, if somehow Smaug overperforms. But no way it does less than 50% with TH:TDOS around the corner to rip of some Imax screens and the other small competitors.
That's some fall. All Twilight movies had better post TG drops. The reason for this bad drop might be because of it's über succesful weekend and weekly numbers after that little underwhelming OW.