The biggest issue is that memory isn't stored in one location. There's certain locations that index memories, but the memories themselves are all over the place. Even if we could replace an area of the brain with robotic components, it's probably more efficient to promote neurogenesis and have damaged sections regrow. We might implant electrodes in the brain for additional functionality, but neurons are so efficient it'll be a long time before we can improve upon them. Regrowing body parts will be preferable to replacing parts, and we'll only add robotic components to augment biology.

I think we'll see biology used in computers more than we'll see artificial parts replace biology. Researchers already use neurons to act as nodes in neutral networks with promising results.