N-key rollover is pretty standard for higher-priced gaming keyboards, but it's still far from universal.
For example, the average laptop keyboard or membrane keyboard is unlikely to have it - and that's exactly what people will be playing casual splitscreen games on.
Clarification: it's standard for gaming keyboards, which tend to be more expensive. It's not like that cheaper gaming keyboards don't have it (even ~30 USD keyboard has one, if it's advertised as a gaming keyboard).
