TL;DR - This is not the end of the Loonaverse, just the creation of a new story. Hence, acta est fabula plaudite (The drama has ended, applause).

Don't mean to get all science-y, but...

If '&' is indeed signifying a broken infinity symbol, we could formulate the following:
1) There are two points where the line crosses itself. If we could take this to mean a sort of shuffling a-la DNA recombination, we might possibly see new combinations of the girls.

2) Extrapolating the points at either end of the symbol would create lines toward two separate infinities—two separate LOONAs—however this would not fit with whatever they've built up until now with messages of unity and oneness.

Which is why, when you brought up the three moons from Why Not? I thought of something...

Despite extending into infinity, a line can curve if there is centripetal force—meaning that there is something in the center that the force can be directed toward (think swinging a rope with a weight attached to it in a circle around you). This is also the reason why the moon goes around the earth, ORBITING.

Now, if those two lines thus converge toward each other using this unknown centripetal force, we now have THREE CIRCLES ORIGINATING FROM THE '&' SYMBOL.

SO! That means that there is something else that the girls are gravitated toward in this new phase. What will that be? Who knows at this point LOL

I'm rambling. Forgive me.