Destruction of the pale tree
i think you’re deviating way too far from the scope and reach of a fantasy MMO.. i personally don’t think anet has any plans for space-related anything
Spoilers….
There’s another pale tree somewhere in the world, you even meet a Sylvari that is from that tree if you choose a certain option in character creation.
I am guessing that if the Pale Tree were destroyed all Sylvari would become members of the night court and being unable to reproduce would eventually die out and become extinct.