Dunno, if you ask me, it is just a shame for original trio to be completely gone forever, especially since they weren't around since 80s, if we only talk about anime.
Plus, even after all this time, they are still the most iconic characters in franchise, not counting major supporting ones.
I mean, sure, their fate kind of seems bittersweet, romantic, and mysterious, but maybe something could be done with the whole center of galaxy, black hole thing, like where they ended up in the future, or rather current time of next main series.
...
But then again, their story IS concluded, but being around as supporting cast, with maybe Minmay finding someone for herself...
Damn it.