iFMagazine.com talked to X-Men: The Last Stand screenwriter Simon Kinberg, who revealed that specific characters were saved for the Wolverine spin-off. Here’s a clip:
WOLVERINE doesn’t exactly come after X3 so what happens to him is not terribly relevant to his own movie. We did talk about a couple of characters that they wanted to save for the WOLVERINE movie spin-off. I can’t tell you who they are, but there was really only one we wanted to use for X3, and they said they’re not going to have a big enough part to risk losing them for WOLVERINE. Sabretooth will be in there, but I don’t know in what form. I think his relationship with Wolverine is under explored.
You can read the full interview at the link above.