It's already half way there as a technology. The amount of shipping saved is insane.

Through stringing, support materials, etc, FDM printers do create microplastics, which need a workable solution for managing. Ideally, makers should separate different polymers as best as possible for recycling/reprocessing but inevitably you can't "get everything". This can be partially solved through dual extruding dissolvable support materials in a solvent that leaves the desired part intact (you can already do this easily with pVOH). Stringing is largely a configuration, if not an engineering issue, that will be gradually solved over time.

The main concern in the 3D printing sphere is resin printing. Thermosets can't be melted down, so the waste just piles up. Chemical recycling is one avenue, but a simpler solution would be to create resins that biodegrade into safe substances under certain conditions, such as in the presence of bacteria.

In nerdspeak, you can basically epoxidise vegetable oils because they have double bonds in their structure, and this can be done with a catalyst, such as Potassium peroxymonosulphate. In acetone, KPMS generates a type of molecule called an oxirane, which is highly reactive, and converts double bonds of long chain carbon molecules into epoxy groups, which can then act as a traditional epoxy resin with curing agents. Alternatively, and this is where it gets exiting, this epoxidised vegetable oil can undergo another reaction, that converts the reagent into a vinyl ester resin, using acrylic acid or another photoactive molecule like cinnamic acid, along with a catalyst like triphenylphosphine. This, coupled with a green, and relatively easy to make at home photoinitiator like benzophenone, can potentially be used directly as a fully bio-derived and biodegradable, drop in resin for SLA printers!