He's often said that his strategy was to do cool stuff with Apple's newer APIs to maximize the chance for his apps to get featured (eg. the magazine with newsstand).
So whatever Apple announced at WWDC could be a nice hint towards his next venture :)
I released a new podcast app a month ago and it's been doing well to date. Not to compare myself with the aforementioned :) Just saying that if you take the time to understand people's pain points and put a new spin on an old paradigm, there's still opportunity in any area.
Also, who said a podcasting app can't have recurring revenue? TuneIn just raised $25M today and we can be sure it's not for 99 cent app sales. (Not exactly podcasting, but same ball park.)
All depends on where you think we are in the market for podcast apps.