Making a Palpatine cliffhanger in TLJ seems to be a popular idea right now, but to be honest I feel like that would be a distraction to the conclusion of that story.
The one thing I do like about the current placement poppasketti and others are attempting is that it basically has the broadcast go out immediately after the death of Luke Skywalker, which seems to be the reason why Palpatine has once again been pulling the strings in hiding. The primary goal of Snoke and the First Order was to destroy Luke, so his radio broadcast could be like a way to announce his return after the death of his last, great threat. Any reveal before that would feel too soon imo.
But, I feel like it does take away from Kylo Ren’s “ascension” a little bit. Kylo Ren literally just became Supreme Leader and then immediately we realize there is another big bad making his way on stage, never giving Supreme Leader Ren a chance to shine. I do like the general foreshadowing throughout the trilogy though. Maybe I just don’t like the idea of ole Palpatine making a whole radio debut!