"Pacific Rim 2" Script In Development

Guillermo Del Toro is currently teamed up with Zach Penn to write the script for the sequel. Regarding the script possibly being a prequel to the 2013 film he says:

Some people were wondering if we were going to do the prequel. I was never interested in doing that first wave of invasion. I’m going for very new, very crazy ideas on the second one, which are very different from the first one — but you will get really great spectacle.

 Source: Buzz Feed