Wow, I did not even know it was announced!
But F2P?? They already said about it? I mean... I know every free to play game, specially high calliber like UT charge for something else. What will they charge? Just aesthetic stuff?
Epic themselves won't charge for anything directly. They're going to put out a base game for free and eventually have a community marketplace where people can give or away or sell skins, maps, and game modes they make themselves.
Where they plan to make money is taking a commission from the community marketplace, the UE4 subscriptions needed to develop stuff, and perhaps some paid resource packs for people to use in their own projects.