I know this isn't exactly what you mean, but AI is actually being used right now to help train AI. I think the OpenAI guys used it to supplement their human reinforcement learning.

Google Deepmind allows agents to compete against themselves in a type of natural selection process to produce AlphaZero.

Nvidia is using AI in limited capacity to design parts of it's latest chips.

So I know you probably mean on a whole different scale where the AI can take over the whole process of training itself, but in a limited way right now AIs already kinda are being used to build AI. And they are already speeding up progress because of these examples and more.