Humans do die eventually though, which is an even more severe form of obsolescense. I don't think they'll be AGI either, but that argument doesn't seem super compelling.
On the other hand you have the old saying "science advances one funeral at a time", indicating death solves at least as many problems as it causes.
(the point being that old, powerful professors have more than once blocked progress in their fields for decades. And only a funeral, eventually, solves the problem ...)
training cannot end for LLMs intrinsically. it's not some fixed cost. it's an ongoing one.