The mysterious, highly aggressive race of insectoid aliens known as the Thargoids have previously been a staple of the Elite universe, but we haven't yet seen them in Elite: Dangerous. As far back as the 2012 Kickstarter, though, Frontier Developments warned that they were “still around,” and following the discovery of alien artifacts in May of 2015, players began speculating that a Thargoid appearance was imminent.
It was not exactly imminent, as it turns out, but recent events have kicked the mystery, and the effort to solve it, into hyperdrive. E:D pilots recently discovered probes of an unknown origin that, when scanned, emit an electromagnetic pulse that temporarily disables nearby ships. The probe also produces a brief bit of audio, and that's where things get really interesting: Players in this huge Elite: Dangerous forum thread (which for the sake of convenience I will drop you in the middle of, near the relevant bit) ran the sound through a spectograph and came up with what looks tantalizingly like a map of some sort—reminiscent of the Voyager Golden Record, perhaps, or the Hiigaran Guidestone if that's more your thing.
People are now working furiously to figure out how to interpret the map, which may not be complete—or may not actually be a map at all. A group known as the Myrmidon Initiative was also recently founded to grapple with the problem of what to do if this does in fact lead to an encounter with the Thargoids (or worse), who are apparently very bad news indeed. The top idea so far appears to be something along the lines of “roll over and beg for mercy.”
Taken together, it's a clear indication of two things. First, it may be sooner or it may be later, but the Thargoids are coming. And second, I really need to start playing Elite: Dangerous.