Yea, I discussed that with TWRA Nashville folks yesterday. They said their sample size for DNA tests in Kentucky Lake have been relatively small so far. So in the grand scheme of things, they weren't overly concerned about the results so far.
It's been nine years stocking KY with Florida-strain. And Kentucky Lake is LOTS bigger than the Chick.
I can't remember details but I know in Chickamauga they were still getting relatively poor results on DNA samples ten years into the stockings (2010). There was actually talk then of whether or not they should continue the stockings, but they did.
It was over the next five years or so that the F1's started showing up in good numbers, including the new state record caught in 2015, 15 years after stocking began. TWRA biologists estimated that fish (an F1 hybrid) to be 11-12 years old, a result of the 2003 or 2004 spawn. Folks I talked to yesterday said they felt reasonably sure they would continue the stockings for at least 15 years.