i highly doubt they'll do the sequel as the same event from another point of view. i know that's one of the theories being tossed around, and as cool as it would be to see something like that, it would absolutely bomb in the theaters. something like that would be best as a short film (or a few short films) used as extras on the dvd release.
the better bet, in my mind, for a sequel would be a completely different city, whole new series of events. but still, i'm not sure how well that would work. i think part of what was so great about this movie was that, going into it, all you really knew was that it was some kind of monster/alien/lizard/bringer of death, rather than knowing exactly what it looked like.
i fully expect there to be a sequel/prequel however. it'd be hard to not want to follow up on the movie that had the highest January debut ever.