User blog comment:Mr. Joshamee Gibbs/Jerry talks about P5/@comment-1140008-20130130012943/@comment-1984959-20130130054333

Assuming this is the only source where the interview takes place... I don't think it said that Nathanson's writing a new script. Make note of Jerry's comment: "I think we have a terrific story. We're working with the screenwriter right now named Jeff Nathanson." He never made clear on if Nathanson was writing a new script(though it's quite possible), or whether Terry is out or not.

I'm willing to bet that Terry is still involved somehow; if he isn't in the screenwriting process, he would still at least be an exec producer(like with OST). Though I think he might still have some credit for the story - note on how Nathanson usually has a side-credit in terms of sequel films(Indiana Jones 4 and MIB 3). However, as of right now, it's a case of Shroedinger's Cat, as Terry himself said in a posted on Wordplay.

Only time will tell before we know for certain. One can only hope.