I think it is doable in under 5 years, but this critically depends on the resources invested by DM and other DL orgs. Deep RL is hugely demanding of computational resources to iterate your designs - for example, the first AlphaGo took something like 3 GPU-years to train it once (2 or 3 months parallelized); however, with much more iteration, DM was able to get Master's from-scratch training down to under 1 month.
Now an AG researcher can iterate rapidly with small-scale hobbyist or researcher resources, but if they had had to do it all themselves, Ke Jie would still be waiting for a worthy adversary... When I look at all the recent deep RL research (
https://www.reddit.com/r/reinforcementlearning/ ) I definitely feel that we can't be far from an architecture which could solve SC2, but I don't know if anyone is going to invest the team+GPUs to do it within that timeframe. (It might not even be as complex as people think: some well-tuned mix of imitation learning on those 500k+ human games, self-play, residual RNNs for memory/POMDP-solving, and use of recent work on planning over high-level environment modeling\, might well be enough.)
\ "Learning model-based planning from scratch" https://arxiv.org/abs/1707.06170 , Pascanu et al 2017; "Imagination-Augmented Agents for Deep Reinforcement Learning" https://arxiv.org/abs/1707.06203 , Weber et al 2017 (blog: https://deepmind.com/blog/agents-imagine-and-plan/ "Agents that imagine and plan"); "Path Integral Networks: End-to-End Differentiable Optimal Control" https://arxiv.org/abs/1706.09597 , Okada et al 2017; "Value Prediction Network" https://arxiv.org/abs/1707.03497 , Oh et al 2017; "Prediction and Control with Temporal Segment Models" https://arxiv.org/abs/1703.04070 , Mishra et al 2017