If it never happened to be a Neptune Pluto would not have been discovered when it was and the way it was, since it was a matter of chance when looking for the responsible of faux anomalies in the orbit of Neptune. No Neptune, no anomalies (real or miscalculated), no discovery of Pluto.

The order of the discoveries of KBOs would possibly be a different one from the one in our History, another KBO would have been discovered first and been termed "the 8th planet" (No Neptune so it would be 8th and not 9th), and now it would be demoted.