I'm holding out for ign's info being wrong about the plot. It's not that I think the world getting curbstomped is a bad story or somehow invalidates my New-Com "achievements" or anything like that. I'd just like for the games to be connected somehow rather than just an immediate do-over.
How I would have written it: Everything happens as in EW. Volunteer goes into wormhole. Volunteer is gone. Aliums seemingly give up after the Templeship is destroyed. Meanwhile, earth is ravaged by the after-effects of the war. Remnant alium left-behinds, chrysalids all up in the everything messing up the ecosystem, meld-poisoning of the environment leading to waves of strange and debilitating mutation in people and animals, but also more lethal mutations of microorganisms - new plagues spread through the population centres, evolving quickly to counter existing countermeasures. People panic, civilization quivers and threatens to crumble, nations abandons any pan-humanitarian unity the invasion instilled for infighting and wars over resources and protection like never before, the new advances in technology and psi-logy causing terror and devastation. The x-com project is all but dropped and stripped to the barest of bones. Things are looking pretty bleak for the world.
Then the Volunteer returns. Like a great messianic figure she promises to save humanity all dangers as long as it follows her - she saved humanity once, she will save it again. She will even save humanity from itself and create a better future. Advent is formed. People flock to Advent's compounds, where they are offered safety from aliums, war and fighting in general, and gene-therapy to counter the mutations and new diseases. To defend humanity... To improve humanity. One by one the governments of earth fall into step behind them, either through domination by the Volunteer's psi-powers or just through the sheer pressure of her millions and millions of followers.
But x-com remains. They know the Volunteer came back changed. They know that their fight is not over. They know that even without the world's support it is a they still have a war to fight. They know that at this hour they are needed more than ever before. Vigilo Confido. Welcome back, Commander.