so if caliborn is from the new universe the kids and trolls will make, do cherubs only exist in that universe? and is the troll planet that cal's mom destroyed the one that the trolls will bring back the race to? so we know the trolls will get decimated again?

Calliope’s father was the one who destroyed the troll planet and yes, that panel is proof that Kanaya will be successful in rebuilding the troll race in the new universe. We don’t know that that was the only troll planet though. Whether or not cherubs only exist in that universe hasn’t been answered in-comic.