Jeez that’s a tough call. Really.
WoW is in uncharted territory nowadays. It’s been the king of the MMO Hill for nearly two decades. We’ve never had anything like that happen before in the realm of gaming entertainment.
I’ve read recently folks made point that there are limitations WoW faces due to a dated engine. At some point that would need to be considered.
A new game Vs. an upgrade would be equally expensive.
But, Bliz just announced a new MMO, didn’t they? I’m not feeling like they would extend themselves into a second WoW any time too soon.