Yes that's very possible. But I do know for a fact that Chinese working at security companies in China are already afraid to visit the USA.

Anyone working for Huawei in security visiting a hacker conference is going to have troubles getting a visa, even before this. I think this announcement is just for show.

There's also a language barrier -- a lot of engineers in Chinese companies aren't as fluent in English as would be necessary to have a good or productive time at DEF CON, so it would have to be more senior/management type people.