Last year was the most profitable in live-music history, with $7.3 billion in tickets sold, twice as much as a decade earlier. This year, expect that number to get even bigger. To fend off competition, festivals and artists are incorporating innovations from virtual reality to marijuana vendors. Recruiting millennials is key: Bonnaroo recently rebounded from a dismal 2016 after doubling down on EDM and hip-hop, moving even further away from its jam-band roots. Here's more of what to expect.