A surge of 2000s-era sonics, a hardening industry line on AI and a whole lot of familiar names are set to influence mainstream music next year. Why it matters: Industry insiders say competition will intensify next year as labels, platforms and artists balance innovation with retro sounds. Execs from iHeart Radio and Amazon Music told Axios which trends they expect to see next year. Prediction 1: The early 2000s band craze will return. “I think…