I assume it will disappear to the air as CO2. Let me know if I am wrong.

Robert above is right: at 1000 ºC in air all the carbon would burn (even at 800 ºC I would expect same result). At the end you would probably end up with a few ashes.

If you want to activate it more, milder conditions between 300 - 500 ºC are recommended.

You can see some typical TGA here in ResearchGate (link attached). Notice the combustion temperature

This is a burning (combustion)  process. Active carbon with the known porosity will gradually oxidized and mostly the transition to the oxides start above 650-700 oC. We actually use this process to clean crucibles with residual carbon from previous experiments in thermal analysis. 

You can see this in a TGA test under air condition with your preferred heating rate.

Thank you very much. You are right, it is burned partially.

I have done this before and your product is just ash that has lost its previous function as activated carbon.