I know that the Mark Levine Jazz Theory and Jazz Piano books were widely used theory books in jazz instruction and almost considered the standard. However, they are both over a quarter century old now. Have there been widespread evolutions in jazz theory since these books have been published? If so, what are some of them? How has playing changed from a theory perspective since the mid 90s?
Although this change isn't necessarily "widespread" yet, one change we are starting to see is a shift from "vertical" thinking to more "horizontal" thinking.
For years, jazz pedagogy was very much focused on the chords (hence "vertical") as determinants for what scales to use when improvising. This emphasis on chords sometimes obfuscated the small changes in voice leading between two harmonies. As a really simple example, consider the chords Cm and A♭/C. Written this way, it's easy to miss that the only difference between these two chords is a G moving to an A♭.
As a response to this vertical focus, some recent authors—most notably Dariusz Terefenko—have pursued jazz theory from a voice-leading (almost Schenkerian) viewpoint that emphasizes prolongational structures in jazz as opposed to the chord-by-chord approach.
But as I said, this new view isn't exactly widespread yet, so it's unclear if this is the new path for jazz or not. My sense is that jazz is still very vertically minded.
Terefenko also has discussions of post-tonal and atonal jazz, something which I'd never seen before, so this may also be an example of a new approach.
Having thought about this question for a while, I would actually say that much of the jazz theory evolution in the past several decades has been more in rhythm than in harmony. Examples of this would be jazz musicians being able to play everything from swing, to funk, to Afro-Caribbean, to J Dilla rhythms and various combinations of those and other styles.
For that I'll reference the sections in the recent book Dilla Time about J Dilla's influence on jazz rhythm as well as Christian Scott aTunde Adjuah talking in this interview about the importance of rhythm.