The trailer ends with this shot https://guildwars2.staticwars.com/img/eod/end-of-dragons-ogimage.51cf1031.jpg
We have already seen concept art with many heads. https://wiki.guildwars2.com/wiki/Deep_sea_dragon
I'm getting the feeling Bubbles is a two headed dragon and it was called S... because it has two names.
So S... for one head and InsetSecondHeadName for the other.
I think maybe one head is good and one is evil and that's why we are getting mixed messages for the mysterious voice vs the treatment of the largos. Perhaps at this point one head wants to kill the other (which will also kill itself)
"It doesn't have to be this way" is Kuunavang not wanting to replace the siblings. The end of dragons, plural, is their death.