Y'know, it would be pretty funny if all this "Zenos is the big bad of the expansion!" stuff was a smokescreen for Varis coming out of nowhere, Emperor of Hell and Heaven style. Whether it be kicking his own son out of finale or being the/one of the driving forces behind the plot of Pandaemonium, I think it could work.

That said, I really hope they don't "speedrun" Zodiark and Hydaelyn out of the story. There's still a lot of questions that need to be asked, let alone answered, about them.