More likely they just mentioned it.
Seems like a bit of a stretch but I want it to be true! While everything about the Bilgewater event wasn't awesome(imho) the lore was great and I'd like to see the rest of the world fleshed out too!
I think they're going to Piltover for at least a brief time, but there probably won't be an event about it. Although it would be awesome to see something like Cait + Vi versus TF + Graves.
Miss Fortune's biography and Act III both had mentions of Piltover, both related to guns. I think It's very possible for the next event to be Piltover related. Correct me if I'm wrong but
Freljord, Shurima, and Bilgewater are the only properly reintroduced nations with their own event?
So that would leave Bandle City, Piltover, Zaun, Ionia, Shadow Isles, and Mount. Targon all being very possible.
I wouldn't say that Demacia or Noxus would receive their own events because they are both VERY clearly canon and are kind of the major focuses of Valoran. I feel like they couldn't really do much with events on either Demacia and Noxus since there isn't a ton of mystery behind them unlike the Shadow Isles or Bandle City for example, where we know pretty much nothing about them aside from Elise's description of the Shadow Isles (Which I'm not sure is still canon or not) and a brief description of what the Yordles/Bandle City is like.
I have a crazy theory:
and
are going to piltover
... and
is going to Zaun... to "fix" his hand 
Zaun vs Piltover event, calling it now.