But why does it have to be the longest AI winter? I would agree that current NLP approaches do not get us any closer to NLU. They won't hurt either though. They may even help to motivate people. I started working on NLU because the current state of voice assistants is so frustrating...
But why does it have to be the longest AI winter?
Because we have explored both paradigms (symbolic, subsymbolic and hybrid AI)
The research has explored both existing paradigms and no other paradigm exist.
Curve fitting (subsymbolic) is inherently limited.
Maybe we need to reinvent symbolic AI, but almost nobody is working on it, and I'm not aware of any promising research paths/ideas for symbolic AI.
My feeling is that symbolic AI hasn't really been explored that much with modern tools and modern computing capacity. It just needs that one breakthrough to show that for certain areas (IMO NLU) it is far superior.
There's no way of predicting when this will happen, but given the current interest in AI I don't think it will take that long, even if currently there are far more people working on subsymbolic AI.