could be made or is already conceptually general enough to learn everything there is to learn
Universality of neural networks is a known result (in the sense: A basic fully-connected net with an input layer, hidden layer, and output layer can represent any function given sufficient hidden nodes).
Nitpick: Any continuous function on a compact set. Still, I think this should include most real-life problems.
An exact mapping between the Variational Renormalization Group and Deep Learning by Pankaj Mehta, David J. Schwab
To me this paper suggests that deep learning is an approach that could be made or is already conceptually general enough to learn everything there is to learn (assuming sufficient time and resources). Thus it could already be used as the base algorithm of a self-optimizing AGI.