The RIAA can try and sue the providers (i.e. GigaNews, usenetserver) but they are in full compliance with the DMCA, so that will go no where. These companies have lots of money to defend their interest and the-powers-that-be only like easy targets.
And it's impossible to go after individual users on their own because there is no connection to peers like in p2p, only private servers.
In short,
Usenet is 100% safe for the foreseeable future.