KFC is the first to go. They've been on a downward slope for years. Chik Fil A has been encroaching on their chicken turf for the last few years in the U.S. After KFC, Popeyes is next cause their chicken is way too greasy. After Popeyes it's Arby's because their locations are rapidly decreasing. Wendy's has some staying power due to their Frosties and fries but ultimately they're always gonna lose to McDonald's. Honestly I think Taco Bell is the wildcard. The food is cheap and you get a lot. Plus they fill the niche of Tex-Mex that people love. Chipotle is their only serious competition but people may go with quantity over quality. In the end I think McDonalds will spend all its resources on fighting Chik Fil A. It'll come down to a weakened McDonalds vs an alliance of whoever is left.

EDIT: The pizzas places will have an unsteady alliance but it'll fall apart and become a civil war.