What will happen to the rest of Tyria?
For the first few months, maybe. While people fully explore the Heart of Maguuma. But once that’s done and we’ve got new LS being added, I don’t see it being any different than it was before.
You’ll also have people slowly leveling up Revenants as some one want to use Tomes or have Tomes. Or leveling up other professions to see the specialization. I know I’ll likely either heavily research or level up an ele of my own before I turn my main into whatever specialization the Elementalists have.
I doubt the zones will be any less active in the long run than they are now.
And of course, there are the people who don’t buy Heart of Thorns.