It's normal to see the price drop after reaching a new high or special target point. It's safe to say that reaching $1000 fits nicely in that category. If there aren't any more hacked exchanges, or worthless fud articles that people take for granted so easily, then the drop will be temporarily and not that intense. In that view, falling below the $800 point would be seen as the price being oversold. Everything above $900 seems fair.
At what point in the history of bitcoin has it made a new ATH and then fallen back below it before going up further. I can remember some short lived testing of support, but I don't recall it ever falling back below until after it cleared much higher levels.