I'm not too sure the nighttrain will be decommissioned, at least it's well listed in the bahn.de-timetables for next year, which were put online yesterday.
note that, despite other regulations concerning daytrains, you may book tickets for CNL nighttrains up to 180days in advance. so in case you're looking for those special offers and are able to commit yourself to a date long in advance, it may pay off to start looking early, as Copenhagen & summer make a popular mix!
p.s. as usual, yet that's only my opinion, I would like to discourage everyone from just booking a seat, at least cough up for a couchette.
Edited by: Nautiker