Development History

Early concepts
Back in 2002, the game concept was originally conceived as "Mobilization". Stardock attempted to license the Total Annihilation engine from GT Interactive to create a new game in the genre.

The basic concept of Mobilization was to take Total Annihilation's core mechanics and combine it with the concept of territorial control and global player abilities.

Ultimately, Total Annihilation was sold to Atari ending the discussion.

Requirements for a massive scale RTS
Stardock published Gas Powered Games' Demigod and subsequently evaluated the potential for publishing Supreme Commander 2. Stardock proposed that Supreme Commander 2 would take Supreme Commander: FA and further refine it even if it mean PC-only. Square Enix ultimately outbid Stardock for the rights to Supreme Commander 2.

With the desire to create a massive scale, PC-only real-time strategy game, Stardock began evaluating the requirements for such a game: By 2012, Stardock had concluded that it lacked the in-house capability to develop such an engine. Since no such engine existed at the time (nor at the time of this writing) licensing was not possible.
 * Engine would need to be multi-core to support managing pathfinding and AI for thousands of units
 * Engine would need to be natively 64-bit so that memory would not be a limit for the engineers, artists or future modders
 * Graphics engine would need to find a way to fully utilize GPUs.

Nitrous
The former engineering leads of Civilization V proposed creating a new type of 3D engine that would be called Nitrous. Stardock agreed to invest in a new start-up called Oxide Games to develop this engine.

Prototype
In 2014 Oxide had created a prototype game with the engine called Star Swarm. Development on Ashes began in earnest.

The general concept for the game remained similar to Mobilization: During the Prototypes, Oxide/Stardock worked with AMD, NVIDIA and Microsoft on Mantle and DirectX 12 respectively. The primary new feature of DirectX 12 was the ability of multiple CPU cores to directly access the GPU with no serialization.
 * Core streaming economic mechanics of Total Annihilation
 * Introduction of territorial control (for future truly massive map cohesion)
 * Introduction of Global Abilities
 * Ability to zoom out on the map

Alphas
Beginning in July 2015, Stardock began releasing Alphas to early testers:
 * July 2015: Post-Human faction added
 * August 2015: Multiplayer added, Benchmark added
 * September 2015: AI added, 2-tier economy added
 * October 2015: Early Access began
 * November 2015 3-tier economy added
 * December 2015: Ice worlds added, PHC Orbitals added

Betas
(note: at time of writing, the betas have not begun, please update)
 * January 2016: Beta 1: Adds Substrate, Additional Orbitals, Dreadnought Veterancy
 * February 2016: Beta 2: Multi-GPU support added, Ranked games
 * March 2016: Ascendancy Wars campaign

Post-Release Roadmap
Stardock has posted a multi-year road map for Ashes of the Singularity. Only a few specifics have been mentioned including:
 * 1) Naval warfare
 * 2) More units
 * 3) More planets
 * 4) More economic structures and refinement
 * 5) Meta game features for Multiplayer including tournaments, empires,