Continuity mistake: In the scene where Hud, Jason, and Rob are hiding in the grocery store, you can see several items toppled over on the shelves above Jason's head. When the lights start to flicker, you notice almost all the objects are now standing upright, only to be toppled over again. (00:21:45)
Continuity mistake: In the scene where Rob is walking on the street in the direction of Beth's apartment (just after leaving the electronics store), you see on the right-hand side of the street the orange framework of a store front. There are parked cars there, including a black Chevy Malibu followed by a white Mercedes, which Rob stands in front of as he points towards the military on the next block. Two scenes later they are (briefly) walking the opposite direction on the same street, which would be away from Beth's apartment. The orange framework is now on the left side and the direction of the parked vehicles is reversed. The black Malibu and white Mercedes are in different positions (as are the other cars on the street). I don't know New York City, so I don't know if the buildings in the background are different. Also, a man in a yellow shirt and tan pants runs past them in both scenes. It is the same man both times.
Answer: Whilst they have made a second film, 10 Cloverfield Lane, it does not have much, if anything at all, to do with the first film. So we aren't told what happened to Rob and Beth.
Alan Keddie