Barclay told Entertainment Weekly that the FX drama's conclusion is "not gonna be what [viewers] think it's gonna be".
"If you think you know what's gonna happen at the end of seven seasons - which is currently what we're planning to do - you'd be wrong," said the exec producer.
"It's not gonna be what you think it's gonna be... it's also probably not gonna be what The Sopranos was. We're probably not gonna end with a black screen. That really irritated me."
Barclay also promised that the upcoming Sons fifth season premiere will be "explosive".
"We're not gonna slack this season," he insisted. "We're coming out guns blazing."
Sons of Anarchy will return with new episodes later in 2012, with a sixth season already commissioned.
> Sons of Anarchy Charlie Hunnam on season five: 'Jax is more mature'
Watch a promo for the Sons of Anarchy fourth season finale below: