Flounder's future
By what I've researched, I believe that in the future flounder may adapt by growing another two eyes on the other side of its head so it can swim like a regular fish and still be able to hide from predators. Having four eyes would also allow it to have amazing eyesight in several directions to look around for sneaking prey.
I think another great adaptation would be to have a "sword" like a swordfish because then flatfish would be able to catch its prey with it if it tries to escape. I believe with these adaptations, flatfish would be third in the food chain after sharks and whales.