Tickets for Electric Picnic 2015 go on sale tomorrow, after what organisers called a "fantastic festival" this weekend.
The three-day music and arts event in Stradbally Co Laois sold out its extra capacity of 41,000 tickets in July.
Kelis, Beck and Outkast are still to play the festival tonight.
Head of organisers Festival Republic Melvin Benn said they had not decided whether to increase capacity further.
"It will happen again for a 12th time in September 2015…We haven't taken a decision on increasing capacity," he said. "Maybe, maybe."