To me the big news is if Sam, Tobey and Kirsten come back. So far we know that there will be one and it is scheduled for 2009, but either way will likely be pushed back to 2010, with Sony announcing that possibility as well. Also, several producers have name dropped Lizard as a definate and Kraven as a maybe.
So the big confirmation is whether the great cast and crew that made the first three special will come back for one more?
I'd say expect to hear it by the end of this year. When though...I don't know.