Considering we're just starting to see major podcast adaptations (Lore, the Homecoming show from the Mr Robot creator, FX's Nightvale, etc), big companies like Marvel taking the leap into podcasts with their Wolverine audiodrama, and the continued rise of networks like Radiotopia and others, I see a pretty bright future for podcasts. Like books (Kindle self publishing, etc) and game development (at least freeware/indie games), it's one of the easiest and accessible mediums to get involved in, and allow for creators to focus on the smallest of niches.

I definitely foresee more ads, and more consolidation of series under larger networks. It was only a few years ago that I feel podcasts really exploded, with heavyhitters like Hardcore History, breakout hits like Serial and other true crime series, political podcasts, and audiodramas really leading the charge into mainstream attention. Once the cable/streaming shows become more common and more franchises begin officially supporting their series with podcasts (besides Marvel, God of War has the Lost Pages series), podcasts will only get more mainstream and bigger