I think Cameron will not be it. And I don't know if I'd really want him for it.
1. His scriptment was not good. Now for all the yelling: "That was 10 years ago!" Yea, but it still was bad, and it seemed he had some flaws as Raimi did with understanding Spider-Man as a character, mostly MJ. So I think just in that I would be worried if he could do. Not saying he could not, but I don't think so.
2. Sony already bought Vanderbilts' script. And Cameron does not like to do things unless its his own script. It happend with T3, Vanja and Kassar wanted him to use Tedi Sarifan's T3 script because they were too cheap to let him re-do it. So I have this feeling that they would not go down that road because Cameron would want to do the script himself. Not use some one elses. Unless he got to majorly re-write it. And Cameron likes to take his time, so I doubt this small window he could do it.
3. Biggest reason of all....Avatar 2. Come one that movie is printing money *I think its Cameron's worst work but...* I think he is more looking at doing his Avatar 2 since this trilogy is his dream. So I just doubt he will walk into another trilogy while he's got his own he is attending to that will make him a bajillion more dollars.
So I just think the cards are stacked against getting Cameron. Yea maybe it would be great, I don't know because I can't see the future. But with Avatar in his pocket, I think he has other things he wants to do. Spider-Man came and went for him, just like T3. And with him and Avatar, he will be busy for a while.