What does it mean in a workers comp case if you get a letter sayinig that you have a hearing to discuss the status of discovery and the status of the disposition of the case in chief?

Discovery is the litigation phase in which each party tries to obtain information from the other.  Discovery may include interrogatories (written questions to be answered under oath), request for production of documents (such as medical records, medical reports, medical bills, documentation of wage loss, etc.).  Other methods of discovery would include request for admissions (admitting or denying various facts), depositions (questions answered under oath).   

The hearing to discuss the status of discovery is to find out what discovery has been done and what needs to be done and the estimated amount of time to complete discovery.

The status of the disposition of the case in chief means what the parties will do to resolve the case; for example, go to trial or arbitration.  If arbitration is selected, will it be binding or non-binding.  If it is binding arbitration, the arbitrator's decision in the case will end the matter.  If it is non-binding arbitration, the arbitrator's decision may not be the end of the case because a party could challenge the outcome of non-binding arbitration.  If trial is selected instead of arbitration, will it be a jury or non-jury trial?  What is the estimate of time for a trial?

These are the types of issues that will be discussed at the status conference (the hearing referenced in the letter you received).