Who has gotten away with murder through acquittal after Casey? Was Baby Lisa, for example, a copycat murder of Caylee? Or Ayla? I don't think what happened to either of those girls was premeditated. Wouldn't hiding your murdered child's body be something anyone would think to do? The Cummings/Croslins got rid of Haleigh's body, and that was back when we all thought Casey was going to Death Row. If anyone is copying what Casey did, it would be in the courtroom. Prosecutors also might be more reluctant to take a case to trial after Anthony, or to "over-charge".
ETA: Are there actual examples of children who were killed because Caylee was? It would have to be premeditated and you would have to be a pretty messed up person to begin with to plan and carry out your child's murder.