I hadn't heard if it passed, but there was a news article recently ( Even linked further back in the thread and has its own thread, I believe ) about a proposed measure that would cause the rights to "dead" online games to expire if unused after a few years. But I believe it basically only grants a form of "fair use" protection to freely run private server emulators.
I believe you are referring to the Library of Congress exception for abandoned works. That would apply to single player games, but not online ones. The reason is that the law would allow people in legal possession of the software to continue to use it if they could declare it abandoned. In our case, that would be the game client. But it would not include the game servers, because none of us were ever in legal possession of the game servers. And while the exception would theoretically allow someone to reverse engineer a server, they could not under that exception reverse engineer the game content because that would still be protected by copyright. Reverse engineering server software doesn't violate copyright, because you aren't copying the server software code, you are creating something new that just happens to behave the same way. But recreating the missions and playable content would be duplicating copyright protected works, which would not fall under the exception to allow players to use the software they possess. And unfortunately the playable content doesn't exist within the game clients to leverage.