Here's the official announcement from Tamaro on Facebook:
As you may have already heard, as of the end of Season 4, I will be leaving as R&I's show runner in order to do new projects, though I'll be continuing on the show as a consulting producer. Creating and running a show like this is what we writer/producers dream of getting to do, and I got to do it for four phenomenal seasons. But it takes all of my focus. I have to step away to create and write other shows and films. The heartache for me will be leaving the day to day working relationship I've had with an incredible cast (!!), crew and production team. You know that, though, because you watch the show. Both TNT & Warner Horizon have been beyond great to work for -- and I look forward to working with them in the future.
And the fandom…holy crap…The fans have been especially wonderful -- passionate and responsive. I have a special place in my heart for all of them. My goal was to bring to life, through story, a real female friendship. I've been especially touched by the people who've told us they became friends because of Jane and Maura.This show will be around for a long, long time. Stay tuned to this page. I'll be checking in and helping out.