They'll try to get it on the next flight, but when that happened to someone I know - whole was technically right at the cut-off time, it took about 36 hours for his suitcase to arrive.
Passengers need to check luggage before whatever the cut-off time is for that airline - not right at that time, as my friend discovered - to allow time for the luggage to be security-checked, then brought to and loaded on the plane.