Marvel Studios has assigned Craig Kyle and Christopher Yost to write the script for the third Thor movie, according to Hollywood Reporter.  Kyle is a Marvel Studios Senior Vice President who’s making the transition to screenwriter.  He’s written a lot of animated series and OVA scripts, and executive produced the first two Thor films. 

Yost co-wrote Thor: The Dark World and worked on a lot of geek TV over the years.

This is the second move to a third-in-a-series Marvel film this week; Marvel’s also started on a third Captain America film (see "'Captain America 3' Directors Set").