Steam said my game was being updated, but I checked the Devblog and there wasn't anything new. I was so hyped for a moment, just to realize it was only for a bugfix... :/
I highly doubt a major release would be without warning. Especially knowing how steam likes to do it's own thing with random updates. Subscribe to their youtube chanel and turn on notifications, keep an eye on the devblog, watch for the official 0.18 discussion thread to get locked, and watch for anouncements on this thread. All of those should be indicators of updates a fair while before anything is actually recieved to the steam client.
Did anyone notice that reflections are only applied to the D-series? The roamer doesn't seem to have dynamic reflections...
The Remastered Levels trailer was released a week before 0.17's release. If 0.19 winds up releasing next week, there is a small chance that we may see some sort of a trailer today.