Empire Online recently published a new interview with Joss Whedon in which he speaks about how his planned adaptation of "Wonder Woman" is going:
"I am still writing Wonder Woman. It is very awesome but incredibly unfinished, but I should be finishing that in a little while and then I'll have a better idea of which film is actually going into production. But I can tell you that the film will be about introducing you to Wonder Woman. She'll be wearing the outfit and there will be the bracelets, the golden lasso and Greek gods. She comes from a civilisation where she's rather perfect, so she's the opposite to Buffy in many ways, but she's going through an adolescent rite of passage because she's new to the world".
He also commented more on further "Buffy" adventures - "We are trying to put together a Spike movie - I don't know if it's financially feasible. That's what I've been working towards for the past several months, and I should know fairly soon whether or not something's going to happen with that".