You are correct. Ex-ID was in the process of doing wave 7 audition before the merge. In fact, there's a video about a Indonesian (living in Japan) content creator/vlogger named Jerome Polin who went into Nijisanji's office 2-3 years ago (as part of ID collab with the guy, also video is primarily ID and JP with ID subtitle) and ended up taking a look into the whole stuff, including overseeing a Nijisanji staff doing character design on a character that might've been one of the ID wave 7 design.If we're going to talk about whether or not EN would merge we would have to see, given the precedent of EX-ID, audition cancellation. I think NijiID was in the midst of doing a wave 7? audition when the merge announcement happened and they canceled the audition. The actor-focused auditions for EN closed in early December so I think it's still a possibility EN would have waves.
The merge announcement specifically mentioned that they cancelled up wave 7, so its likely that they are probably still doing audition by then.