I'd be very surprised if whatever licensing deal Six Flags has struck with Warner Bros. doesn't prevent Warner from licensing the property to other North American parks.
That said, it's Six Flags. So, you know, Murphy's Law certainly applies.
With SAW being at Scream Break; I think Lionsgate and SFCorp would've been settling to ensure the IP would be at the event as a constant for a period of time. For both Scream Break; and Fright Fest.
The fact The Conjuring has left, but Saw has stuck around makes me think SFCorp will keep it.