Those stories already started, some Russian mil-bloggers say that F16s are already in Ukraine which is probably copium. But I wouldn't be too surprised if this isn't accidental and Ukrainians re-doubled efforts to take down Russian planes (e.g. via smart and unexpected movements of anti-air installations) in anticipations of F16s coming, they're a lot more useful more quickly if they don't have to operate in contested skies. Every air-to-air missile you don't need to have in your loadout is another air-to-ground one.