If Gravens calculations are correct, carbon dating as we know it today will no longer be reliable by the year 2030. Which means scientists wont be able to use carbon dating to distinguish between new materials and artifacts that are hundreds or thousands of years old.

Can you carbon date something from the future?

In principle yes, but it wont be of much use. Carbon dating doesnt determine the age of an object, but rather how long it (or the organic materials it was made of) has been dead. Carbon comes in multiple forms (isotopes).