I know people's emotions are running high here, and part of me want her charged right now, but it would make no logical sense.
First they don't have a body and they don't know whether to charge her with murder(or what degree), manslaughter(accident because of negligence), or how she disposed of the body and charges surrounding that.
Second under Florida law, when they do charge her they only have 180 days from formal charges to bring her to trial. Since they know where she is, and she is not a going to disappear on them, they have time to get all the evidence tested, and all the searches they feel they need, done. I am not sure they will find a body other than the strands of hair, fluid and gases they already have, but they do deserve the chance to find them.
After everyone has been emotionally invested in finding a living breathing Caylee, it is hard to switch to the mode that there is no reason to hurry anymore. Hurrying will only hurt what chance for justice, little Caylee has.