I just graduated with a BS in materials engineering last month so I feel compelled to give my two cents.
I do not foresee diamond becoming exceptionally more prevalent than it is. Diamond is the hardest known material and is very abrasive and temperature resistant, but also very brittle. The most common industrial applications for diamond is for cutting and grinding. For example, many industrial saw blades are diamond tipped. Diamond is too brittle and expensive to make “everything” (or hardly anything for that matter) out of it. However, I do think diamond prices will decrease in the coming years as scientists improve synthetic production of it using chemical vapor deposition (CVD).
Carbon nanotubes (CNTs) OTOH along with other nanofibers are on the horizon for use in many more applications than seen today. They have an incredibly low density, high tensile strength [IOW a high specific strength], and high resilience. There are already some composite materials reinforced by CNTs such as those used in high-end baseball bats and tennis rackets. Body panels in some GM cars are reinforced by olefin nanofibers.
CNTs also have unique electrical and chemical transport properties. I was a research assistant during my time as an undergraduate working on functionalized CNT-polystyrene membranes for possible future chemical separation applications in pharmaceutical and food processing industries. Here’s a link to an article related to my former research group.
I see that Fast ‘n’ Bulbous expanded on CNTs a bit.
Even the average run of the mill MWCNTs cost $750-$150 per pound these days so macro scale applications are nearly impossible. I do see greater use of CNTs in electronic and chemical transport applications though in the near future. CNTFETs may even replace MOSFETs (metal oxide semiconductor field effect transistors). The price of CNTs will continue to decrease each year but at a somewhat gradual rate.
Nah…like diamonds, ceramics are too brittle and expensive to replace metals in most applications. Usually, industrial ceramics are limited to applications involving high temperature and/or heavy abrasion but weak dynamic forces. For example, tungsten carbide is commonly found in drill bits. Also, there are cermet materials in use today which are a combination of ceramic and metal.
Composite materials were mentioned in previous posts. I certainly think these will continue to be more widely used and cheaply processed because of the desire to have stronger and lighter weight materials especially in fuel consuming vehicles. The next generation of airplanes including the Airbus A350 and Boeing 787 have structures that are mostly carbon fiber reinforced plastic composite materials. Fiber reinforced materials are still expensive to process: imagine trying to weave hair clippings through a wad of chewing gum keeping a consistent distance between strands of hair. That’s a challenge analogous to trying to manufacture composites.
Titanium is also difficult and expensive to process at least in its pure form, but not so much after it is alloyed with other metals.