The game's Alpha also comes with a level editor, which Mojang hopes players will use to "create everything from single maps to whole campaigns from scratch." That isn't to say that the dev team at Oxeye Game Studio are sitting on their hands and waiting for the user-generated content to populate their game, however -- the announcement promises that the team "will continue adding their own maps and game modes to the game as well as continue work on the main campaign."
Like with Minecraft before it, purchasing Cobalt in Alpha (or "pre-ordering" the final build, if you will) nets you access to all future builds of the game, barring the possibility of console or mobile ports. While there is no timeframe for the completed game's launch, the devs set a handful of milestones for themselves, such as the main campaign not showing up until after the game goes "Gold" (read: finished). In the meantime, we'll be sure to let you know when people start creating incredible homages to things they love within Cobalt, as with Minecraft before it.