It's pot luck that time of year. Some years it has been great as early as late November, other times the real snow has not arrived until the new year.
Would love to be more positive for you, but the truth is Pamporovo at Xmas can be a little too early for decent conditions.
I would rate it as 65% yes 35% no so the odds are in your favour, but nothing is certain, regardless of what did or did not fall this Xmas gone.