EW.com reports that in a statement, the network said:
When we extended our multi-year overall deal with Alan Ball in July 2011, we always intended that if we proceeded to True Blood’s sixth season that Alan would take a supervisory role on the series and not be the day-to-day showrunner. If we proceed to season six, the show will remain in the very capable hands of the talented team of writers and producers who have been with the show for a number of years. This is the best possible world for both HBO and Alan Ball. Alan will remain available as executive producer to consult and advise on True Bloodand he will be free to develop new shows for both HBO and Cinemax. Banshee, on which Alan serves as executive producer, is the first in house series for Cinemax and is expected to begin production this spring.
Meanwhile, Ball says in a statement:
True Blood has been, and will continue to be, a highlight of not only my career but my life. Because of the fantastic cast, writers, producers and crew, with whom I have been lucky enough to work these past five years, I know I could step back and the show will continue to thrive as I look forward to new and exciting ventures.
The Vault wishes Alan all the best of luck with his future endeavors and we thank him for giving us True Blood. We have full confidence that the excellent True Blood writing team will carry on his legacy.