Hasn't advertising always been the primary drip of financial resources for podcasts? Aside from a bit more enthusiasm for Casper mattresses than is probably warranted, I don't think your concerns have come to pass.

The great thing that podcasts have going for them as a product is they're super cheap to make (relatively speaking). Podcasters willing to compromise the product by taking on more obtrusive advertising will get outcompeted by those who don't. It's ideally how media sites in general would work, but those are expensive enough to run that most sites resort to intrusive ads.