Burchard died in 1920, and therefore did not see the backlash against sexology and LGBT+ rights driven by the Nazis. Hirschfeld left Germany in 1930, fearing persecution. Their research was suppressed by the Nazis, and Paragraph 175 became even harsher under the far-right.
"Cis" wasn't used again for many years after this, until it was revived in scholarship by German sexologist Volkmar Sigusch in 1991. Sigusch used the term "Zissexuell" (cissexual) to describe people who were not trans.