Why not die Diskussion also?
"Diskussion" is also correct (and arguably preferable).
In an earlier sentence, it was die Rede for the speech. Could it also be die Sprache or is that more often tied to the language (but could still refer to speech - contextual)?
"Sprache" is "speech" in the sense of the general faculty of speaking, not in the sense of an oration.
Das Gespräch is the word for conversation built off of sprechen.