Yang doesn't have presidential aspirations anymore since he knows he can't get elected. People are bigoted towards him and his message, so he didn't get far in either election. The Forward Party nominee will probably be Cuban, Amash, Gabbard, or Williamson.
If Cuban wanted to run, he'd do it as a true independent like Perot 92. Amash would run as a Libertarian. Williamson as a Dem, Green, or with the People's Party. Gabbard is the only one I could see running with the Forward Party, but I could see her also running as Dem (who isn't in the debate stage) or with her fellow grifters in the People's Party.