A short quote that SuperheroHype got from Spidey director Sam Raimi "sounds" like he is, but then again...
"James Vanderbilt is writing the script and I'm excited to read it. I think it's going to be done in a few months... I'm hoping it's as great as our discussions were about it and I'm hoping it feels right for me because I love Spider-Man. I'm hoping I'm well rested enough to embrace it and I'm hoping Sony wants me to do it. If all of those things come together, I would love to do it. There are a lot of unknowns about the future."
Asked how he feels about a re-cast he said, "I'd hate to re-cast anybody in the future, I can't imagine that."
If you take just his words at face value, it sounds as though he's ready and willing to do Spidey 4, but I'm a little concerned about the "tone." I know you can't tell for sure how someone sounds in print, but all the "I hope" stuff is a bit disconcerting. I kinda wonder what he is NOT saying.