There's no way they're porting GW2 to Unreal 5, it's simply too much effort with too little gain. To be honest, Unreal doesn't lend itself very well to MMO's out of the box. I say that as a professional UE5 game programmer myself.
Given the fact they're looking for animation and narrative programmers, I believe you can rule out any GW3 development, as those roles would only be brought in a lot later in the project.
That leaves a new IP, or some mobile spin-off as most likely scenario.