If I'm reading the rumor correctly, it seems that IJ Land would be a "midlevel" upgrade - it'd be more than just an overlay but less than building it from scratch. How that fits in with long term park planning is anyone's guess - particularly with AK being the most "complete" park at the moment while the other three get substantial attention. Even as described, it just feels like it would be a land destined from Day 1 to be bulldozed for something better down the road.
I'd much prefer to see another continent at the park. Although I really like IJ, I don't see how an IJ Land contributes to the overall theme and purpose of AK - IJ is about the character, unlike Pandora which is about the world (which is good, since I can't remember a single character's name from Avatar). Whatever happens, however, I agree with the posts above that DinoLand seems to be on the way out.