They're only within our lifetimes if you require the devices to be the size of modern day silicon chips. There's nothing preventing us from building bigger devices - I mean, my laptop and smartphone's SSDs already essentially act as caches for much larger remote storage and compute hardware.

And given that nature has managed to cram this amazing sentient device into a space the size of our skull, using a pretty inefficient design process, I'd say the problem will be not the quantity of the building blocks, but how they're organized :)