Did Knuth touch on the ability to morph between different designs of a font, or was it simply the ability to do fonts as sets of curves so that they could be resized?
Edit: never mind, I looked up the original paper and find a good description in just the first paragraph. He definitely had variations of the letters in mind.
1982: Knuth's paper "The concept of a meta-font" is published.
1991: Adobe's "Multiple Master" fonts are introduced.
1994: Apple's TrueType GX is introduced. (Later "Apple Advanced Typography".)
2016: OpenType "variable fonts".
Maybe "variable fonts" are better than their predecessors? It's hard to tell. But it's strange for the predecessors not to be acknowledged at all.
Much more information about OpenType's "variable fonts" can be found at https://medium.com/variable-fonts/https-medium-com-tiro-intr... -- discussed on HN at https://news.ycombinator.com/item?id=12501665 . (That article does mention TrueType GX and Adobe multiple masters, but not Metafont.)