Lets assume that we get to the point where one can 3d print pyrex glass (not other glasses - it has to be pyrex). This doesn't resolve the "this piece of glass broke, I need a replacement inline for this 5'x3' manifold."

There is also a very strong bit of "I don't know what the requirements are." A chemist will go to the glass blower and ask for something... they can describe what they're trying to do, but they've got no idea about what they need to actually accomplish it ("I'm trying to create bubbles in a fluid" or "I'm going to be putting a catalyst in an oxygen / hydrogen mixture to examine it while the reaction is taking place"). It is the glass blower that takes those requirements and makes the actual product.

Claiming that in 5 years one will be able to 3d print pyrex glass and glass blowers will go the way of the buggy whip makers is akin to saying that you see a renaissance of visual programming tools and in 5 years programmers won't be needed because you'll be able to have the application automatically generated.

I don't see it.