Ball, who has a contract with network HBO, will stay with the supernatural drama if it is picked up for a sixth season, but in a supervisory role as he steps up work on new crime drama Banshee for HBO's sister network Cinemax.
A statement from HBO read: "When we extended our 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.
"Alan will remain available as executive producer to consult and advise on True Blood and 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."
"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."
Ball had previously hinted that he was considering leaving the show after its fifth season, stating: "I don't know if I have any left in me after that. We'll see."
> Stephen Moyer 'confident of True Blood future'
Watch a True Blood 'inside the episode' feature for the season four finale below (may contain spoilers for non-US users):