Put me in the "hope he doesn't run" camp. Because he stands no chance of winning. Ralph Nader was a great champion of the consumer, but running his never-going-to-win campaign accomplished one thing: electing George Bush.
Green party candidates, same thing. Way to go people, help elect the one party that is bound and determined to steamroll the environment, accomplishing...what...publicity, fundraising?...during the campaign while setting back environmental causes by years if not decades.
Yang isn't going to change the system from the outside of the two parties. He'd be able to get something done, maybe, by being a cabinet member for a Democrat president. Running 3rd party he'll accomplish one thing, making sure the Republicans get elected (I think they will anyway, America being full of Americans, but still)
These people run for notoriety and money, perhaps not in that order.