That's a really loaded question.
There's not much new in terms of what a podcast is. At it's core, it's been traditionally radio format with modifications for video. And as a medium, radio/talk-show formats haven't shifted dramatically since I started doing production 14 years ago. Popularity and delivery medium have shifted more than anything.
The direction an individual podcast takes is really where it's potential and limitations can be found. A podcast with a live/video component and a post-production edited side, will vary greatly vs a product review 1-man-band type of show format.
My biggest concern is always saturation, and the ability to curate quality content to keep the most relevant and quality content in a visible spectrum. YouTube has become pretty muddy. My suggestions keep me in a loop of the same content, and the only way I discover something new is if it's recommended to me, or it goes ultra-viral.
Also the ability to sustain itself. YouTube had a large ad model backing it. People made a lot of money from their efforts. But then as it became more saturated, that translation to income has become more watered down. I see more and more concerns with how to get paid a living wage. Podcast have been a far more direct interaction with sponsors.
We pitched podcast content for TV show productions for years, and someone high up always shot it down. The ad revenue wasn't viable. It wasn't until Serial became crazy popular and break all the records that our bosses started to come around.