I agree with you on the dictionaries. Unfortunately there is no dictionary format for epub yet and Adobe does not have one. My understanding is that the mobile ADE does support tie-ins for a dictionary component. As far as I've seen, Sony has not revealed the format nor do they support adding dictionaries to the reader.
The IDPF is working on a dictionary format for epub 3
, but there is no indication as to when that will be completed. Nor is there any indication as to how long it will take before the industry supports it.