We can't say the regulations directly affected the privacy coins and it will completely kill the future of it because the next level of decentralisation is complete anonymous coins which still has the user base if I am not wrong but the most preferred privacy coin faced some technical issues in the past later governments made regulations which completed delisted the privacy coins from exchanges so price went down and volume but it doesn't mean it will be forgotten...
In future we may have better developed privacy coins and government may support cryptocurrencies with no regulations will make them to exist.