Was reading the other boards and this is a topic on most of them. According to all the others, no one has received their vouchers either. I'm sure it's going to take them a while to get them out. One poster said that they rebooked their cruise for another date right after cancelling the original one. They stated that they have yet to receive the credit on their credit card for the shore excursions they had planned for the original cruise and it's been almost a month. She said she even called her credit card company to see if it had been posted and it hadn't.
Maybe you could get in touch with your TA and see if they know anything or if they could call the cruise line for you. If not, maybe you could call to see if they have an approximate date?
When I spoke with RCCL back in late September, they thought the voucher letters were due to be mailed the 1st of October. Then when I called, and recheduled our cruise, they told me middle to late October.