Sounds like the Green Goblin is set to return in Spider-Man 3 — along with Sandman and possibly Venom!
[FILMFORCE:] The moment Spidey-fans have been waiting for has finally come. Today Sony Pictures released the first official trailer for Spider-Man 3. The trailer only lasts for about 90 seconds, but shows more than either teaser for its predecessors. The short preview is also set to debut with Superman Returns, which opens nation-wide tomorrow. Spider-Man 3 is currently scheduled to be released on May 4, 2007. Read more.
Sounds like a close examination of the trailer reveals a return appearance by the Goblin, the introduction of Sandman, and perhaps the origin story of Venom!