I thought the sequel was canned
If it wasn't officially, it's definitely in development purgatory now. I don't see why everyone chooses to say development heck, because purgatory is a place where there's endless nothing... that's just more accurate.
That article was 2 years old, and most importantly, before Mars Needs Moms totally collapsed at the box office. That's when there were to be a LOT more motion capture Zermeckis films, and the article says that it's still producing the Yellow Submarine remake.
I don't think that movie was canceled, but rather it was righteously struck down by heavenly forces.
Roger Rabbit 2's window of production has closed up completely. We would have had a sequel if Spielberg wasn't so maudlin after making Schindler's List... this was the guy who had the movie about a bunch of Nazis trying to attain the Arc of the Covenant and getting melted. Had Roger Rabbit 2 been made after that mind set, we would have seen it by now.