Recent story boards for Spider-Man 4 have revealed that rather than reduce the number of villains after Spider-Man 3 that we actually would have seen even more. We know for sure that Mysterio was being considered since there were concept sketches revealing it, but apparently Shocker, Rhino, and Stilt Man were also likely to show up according to illustrator Jeffrey Henderson.

: https://screenrant.com/spider-man-4-canceled-trivia-facts/