Closing Date/Rate Lock

We have been in contract since October to buy a townhouse in Clinton Hill. The house is empty as it is an estate. The proper doucments have been with the Surrogate’s Court since October. We can’t close until the documents go through court. So we do not have a closing date yet. Last week the court told the trustees that the documents will likely be stamped in the second half of December. All parties want to close this month and are ready to close as soon as the doucments get through court. In the meantime we have been watching the mortgage rates. Today the rate is at 4.875% with 1 point. This is the lowest we have seen. We’d love to lock in at that rate but the rate would expire on 12/31/09. Is this too risky considering we don’t have a closing date yet?
Thanks!