In a bit of news from left field, Deadline is reporting that Simon Pegg has signed on to co-write Star Trek 3 with current writer Doug Jung (Dark Blue, Diamond). The script is being re-written after Paramount was so unsatisfied with the Bob Orci draft that they fired him as director (replaced with Justin Lin) and essentially removed any influence he has on the film probably only retaining the producer credit for contractual reasons.
Simon Pegg will retain his roll as Scotty in the movie. Past writing efforts from the actor include Shaun of the Dead, Hot Fuzz, and The World's End. If watch those (low budget) movies Pegg's brand of humor clearly comes across while retaining strong characterizations and interesting situations. They were also all co-writing efforts. Combined with Pegg being a long time and vocal Trekkie and one of the few new movie actors to show up at conventions and the whole thing comes across as a win.
It will be interesting to see what the final product will be which is rumored to be set at an undetermined point in the Enterprise's first five year mission. The new duo is probably already neck deep into a draft as Star Trek 3 is aiming for July 1, 2016 release date so filming needs to start by mid-summer if want to allow enough time for the likely heavy visual effects post production process. It seems like a ton of time but generally on big budget films the pre-production process, including the script takes about 6 months to a year, filming is around 3 to 5 months and post-production tends to average out to a year (but on VFX side it is really just a continuation of pre-production) so the average summer film needs about two years or more from start to finish to nail a release date. Star Trek 3 is now has 18 months plus whatever time pre-production started minus whatever time and effort was lost with the script and director changes. It is still do-able, its just going to get harder to hit the release date the longer they take to start and complete principle photography.