I never understood the concept of trying to keep a cool season grass in the South. Sure it will stay green in the winter, but from spring until frost it is an uphill battle trying to keep it alive. Can't fertilize it to keep it green, can't water it enough to keep it hydrated. Ornamec + Turflon if you must hurt the bermuda, however this is a multiple application over multiple growing seasons type of program. There might be a good reason why the neighbors all have bermuda. I do know that the seeds for bermuda remain viable in the soil for a long time. In your shoes, I would start mowing with a reel, fertilizing at 1 lb of N per month during the growing season of the bermuda, then nuke the last of the fescue that remains with Revolver or Image. It is probably easier long term to keep the bermuda. As an aside, the extreme heat and drought in the South is not a fluke or a rare occurrence. It is probably related to a long term weather pattern known as the Pacific Decadal Oscillation. In plain English, that means that the South gets hotter and drier, my part of the world gets cold, windy and rainy. I am getting an abnormal amount of wind and rain for August in Hawaii. It is also way cooler than what is usual. Has not gotten up to 90 here yet, where in years past, I see 90 starting in March. This weather pattern usually persists for at least 10-20 years on average, hence the name.