Due to the fact that every single computer-related community, even large sites like anandtech, tomshardware, etc. are talking about mining this means that every single 3xxx 68xx that is sold it is actually used for mining, let it be professional miners or gamers. Due to the hype and media cover, everybody knows about mining and everybody is mining. So yes, the vast majority of new hashrate is from 3xxx 68xx ... ASIC can't just come ouf of the blue ...