As a few mentioned, they don't send personalize monthly vouchers in December. It was also mentioned in Dirk's Open Letter sent October 31st.
That being said, last December 31st, PA did send out a one-time use $75 voucher to everyone which could be used on any orders $150 or higher. While there's no guarantee that it will happen this year, it might. A lot of the plugins that had been on sale during the X-MAS CALENDAR sale were also on sale during the MEGA-Sale between Christmas and New Year. That being said, who knows if the same plugins will be on sale after December 25 (i.e. LION) this year.
For reference, here are the plugins that were on sale last December 31st: https://web.archive.org/web/20181231095 ... ducts.html
(Again, there's no guarantee that something similar would happen this year, specifically for LION which was only released this year, but it's a possibility)