JAL's smaller cabin attendant union plans to strike on Dec 24 and 25.
JAL has ~5400 CAs and this union only consists of ~870 CAs. Not sure about how this will impact JAL operations but during previous strikes, only domestic operations were affected and sometimes the unions even cancel the planned strike.
There will be the monthly JAL press conference today, in which JAL plans to announce the approval of the restructuring plan by the Tokyo District Court. Might have more information after the press conference.
I would say you have nothing to worry about for now if you are traveling internationally during that period of time.
Source: SankeiBiz (in Japanese)