I'm in a private Twitter chat with a majority of the main NMS Youtubers (Cobra TV, Dan Before Time, Get Indie Gaming, Sirian Gaming, etc) and we're all speculating that this could be an actual RElaunch of the game. Our line of thinking is simple-
A couple months ago, an "Old Build Test" popped up on the SteamDB, no updates or anything else. Very strange. Sean was quoted as saying that when developing the game, they had one central server that housed the main build of the game, while the other devs had their own to test their workings before uploading it to the main build. I'm wondering if we never actually got the main build, or "Old Build", but a more vanilla version of the game at launch because they were "Running out of money" (Seans words) and time, and the features that didn't launch with the game just weren't up to par with their standards.
Then with the two updates we got since launch (Foundation and Path Finder), they were more unceremoniously, launched days after a trailer for them with no hype build up.
NOW, we have a thoroughly thought out, paid for ARG with actors, websites, broadcasts, telephone number, emails, etc building hype for the next update, with talk of the Atlas, historical lore for leading up to the actual game, portals, multiplayer or co-op, and other cryptic things. Yesterday's ARG devlopment points towards server and cloud utilization as well.
Just my two cents, but that sounds like a solid theory.