Intended by Original Series creator Yoshiyuki Tomino to be the last Gundam Series.
"Turn A" is the is the universal quantifier used in discrete mathematics: meaning that the Title of the Series is actually "For All Gundams". This is proven throughout the Series, as it is eventually revealed that the "Dark History" of the Correct Century is a combination of Tomino's Universal Century, as well as the Alternate Universes of "Kidô shin seiki Gundam X" (1996), "Shin kidô senki Gundam W" (1995) + Shin kidô senki Gundam W: Endless Waltz (1998) (V) & "Kidô butôden G Gundam" (1994).
Several References are made to previous Gundam Series: The Turn X Gundam uses the Shining Gundam's trademark attack, "Shining Finger". The Kapool from "Kidô senshi Gundam ZZ" (1986) reappears.