The next (and last) letter is C. Just as a countdown counts backwards, this series is "countdown" spelled backwards.
X is the next letter I think!!
D
W
D
The next letter is D. The pattern is every fourth letter. Ie. a b c D e f g H i j k L m n o P and so on...
Next three letters are: e n d
d
R
J. Those are the initials of the months, backwards from December through July. The next would be June.
S, S, O, N, D etcItalian:UnoDueTreQuattroCinqueSeiSetteOttoNoveDieciECC
It looks as if every third letter is an "r"; the remaining letters are in sequence.
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern D-N---ND. That is, eight letter words with 1st letter D and 3rd letter N and 7th letter N and 8th letter D. In alphabetical order, they are: duneland
T (letters without curves)