The idea of a full scale war with the thargoid world is nice, however there's one problem: the whole thargoid invasion thing was made to appeal to only a small fraction of the player base. Most people just don't bother because it's too expensive, too time consuming, to far away, to complicated, and not rewarding enough.
A paid update that's mostly focused on a niche activity that most players don't bother doing would be a terrible idea. They would need to make thargoids fighting a more widespread thing first, and then they could think about doing it.
Except this wouldn't only benefit combat-oriented PvE, AX players. The fleets will need materials, the new worlds will need mapping, and even PvPers might have something to say about it. It adds an element of "end-game" to every aspect of gameplay currently available.
I take it you haven't seen the leak? 2020 will bring space legs and base building.
Just took a peak. Well, like I said, here's hoping.