"It's true that we mostly refer to "les libéraux" or "les conservateurs". In writing, however, the parties are not unfrequently referred to using their three-letter acronyms, "PLC" and "PCC" (those parties' names are officially composed of three words, unlike the Parti québécois, for instance). "
So, if that's the case, if the NDP became the Democratic Party of Canada the in French it would be Parti democratique du Canada and would be referred to as "PDC" - so what's the problem?
Honestly, one of the worse things about the NDP is the party's penchant for endless navel-gazing. All things being equal, I'd like to just have a really quick up and down vote to drop the word New and become the Democratic Party of Canada PERIOD. Get it over with and then never have to endure any more discussion about what the party's name ought to be. I think dropping "New" is a good idea - but only if it can be done really quickly and with as little discussion as possible - its not worth the effort if it means unleashing a never-ending process of navel gazing.