Yes, you are right, but there is something I wanted to point out.
I am pretty sure Minmei is showin on Earth in Macross Plus. I believe during the 3rd act, or close to the end of the 2nd Act. She's at the Sheryl concert.
So, how does she return to Earth? Macross Plus takes place what? 20 years after DYRL? Where's Hikaru? Misa?
From a story telling standpoint, Hikaru and Misa don't move the story foreward, so they were never shown.
Having Minmei at the Sheryl concert was another metaphore, a passing of the torch from one legend to another. At least, that's what I got of it.
Back to Hikaru and Misa, I think it would be very cool for the next Macross Saga to show us the story behind this expedition. Of course, some fans won't like this, but I think the majority of fans I know would be in favor of such a tale. Food for thought.