What these movies will be are sequels of older films.
What these movies will be is sequels of older films.
What these kids will be are late for school.
What these kids will be is late for school.
IS either are/is applicable in both scenarios? I'm not a native speaker, and for whatever reason, in the first case, I feel like are is the right choice, whereas in the second one, I feel like is the right choice.
Am I right or wrong? Or is is or are the right word for both cases?