Desperate for Advice

I am a parent of an exceptionally smart 21 year old son . He got thru High school on his High IQ up until Sophomore year when his grades dropped and we realized he had ADD , 

He always loved to play Video Games from an early age . 
He was athletic and outgoing , played music , until he needed 2 knee surgeries one after the other in High School , he was out for 2 seasons , this is when he started playing more and more Video games . After that it was all down hills , stopped going to school on time , grades suffered , Junior and Senior year were a struggle for him . With all this he was still able to graduate with 18 AP credit hours and a perfect Math ACT ,he received a good scholarship to a good university , all while gaming online all hours of the night . We tried Therapy before sending him off to college , he did well his first year . Second year he started League of Legends , stopped going to classes , stayed in his dorm room weeks on end without ever leaving , when we realized this we went and picked him up and brought him home . Drs said it was a Bipolar Episode , He took a semester off to get therapy and meds , was taken off Bipolar meds , the Dr felt he was not Bipolar since he had some side effects from the meds and no current signs of Bipolar . He did well with only Vyvanse 40mg  , got a good job at as a pharmacy Tech signed up for classes at the community college close to home, he started talking about going into Pharmacy . Then he got more involved in Super Smash Brothers Melee , he justified that it was a more social gaming experience then what he was addicted to before , as he has to physically go out to venues and meet people in order to play . As he got better , he spent more time watching streams and more time playing at odd out of the way places where gamers meet . He then decided to quit his pharmacy job as it was getting in the way and taking up to much time, he dropped his classes at the community college .About 2 weeks ago he announced that he wants to move out and be independant , rent a room from a friend and be a professional gamer by get paid to stream and win tournaments for cash . My spouse and I feel like we literally lost our son !!   It was one year since we picked him up from College and he was back in the gaming addiction where he was when we picked him up .  Is the gaming causing his unrealistic thinking or is it a mental illness that is not being treated that is causing him to give up everything and live a life of a homeless person who plays video games and gets pennies from tournaments ?  It is an awful vicious cycle , he came home because of gaming , started getting back on his feet , only to be lured back into gaming  by so called friends who encourage him to play . The lure and encouragement and success when playing and winning is the most pleasurable thing for him . He can easily drop his values , his ambitions , his family , his humanity , his hygiene to play video games.   He has an appointment with a highly recommended psychiatrist in 2 weeks , we are waiting to see if he will have a diagnosis that can be treated or if he is being a rebellious college dropout who wants to be a pro gamer .  He wants to move in with 2 other people and set up streaming where he will play 8 hours a day to improve his chances of winning tournaments. He does not seem to realize that he will need a real job to pay rent , buy a car , eat food ??  If it is a rebellious College drop out we are at the point where we will cut him off and ask him to leave . We have already told him we do not support his choices and have stopped giving him any money , we took the extra car away and have been keeping it with other family members and told him he can not use it. If he has a diagnosis with prescribed meds , I don't know the right way to approach things , they say the gaming is a result of an illness , I truly feel the illness always follows the gaming , Illness being unrealistic thoughts and no emotions towards anyone except when gaming , he basically becomes a zombie.   Should we still give him an ultimatum and ask him to leave and not support him if he comes back with a diagnosis of Bipolar and if he still continues to attend gaming tournaments  ?? Our main goal is to get him to stop gaming in a compulsive manner and work and get some realistic goals ??  All advice on this is greatly appreciated .