It's all down to the programming. We're hoping to get as much of the game done before we get an AI in the game, as soo many game components will eventually rely on the AI implementation. It's not just simply about combat or having someone to play against. The AI would need to make decisions on diplomacy, intel, research, ship movements/exploration/ship ranges, colonisation, system management (what to build, provide food, provide energy, defenses...), resource management (I need Dilithium to build...), reactions to random events, and so on.

That will take an incredible amount of coding, and since many of the game components that the AI will link into don't yet exist or are incomplete, there just isn't any point in building an AI yet. So i'm sorry to say, but it's going to be a while. But it will be done.