I think the title is quite overoptimistic. 3D printing is starting to take off because the cost of 3D printing is going down, and making it feasible. 4D printing is going to be far too expensive for practical application for a long time, and is therefore far from making 3D printing a thing of the past.
Feh. I've got prior art on all of this. We used to scrunch down the wrappers on drinking straws, put the wrapper on the table, then add a few drops of water. =)
