Serial has changed the way podcasts are perceived. While they used to be seen as amateurish and niche interest, Serial has shown that they can have mass appeal and a more professional polish. It is likely that this success will encourage other podcast makers to follow in the footsteps of the crew and create similar work which will be popular with the public.
Yes, I definitely do believe that podcasts will become more popular due to the success of Serial. It has really taken on a life of its own by this point. I think more and more people will become interesting in the format because of this even though it has been a relatively popular format for at least four years now.
Like so many Internet phenomenon and forms of media, podcasts began as a relatively nerdy thing, and not something that your average Joe was likely to listen to or even know about. But with a noted NPR journalist having made this very interesting podcast, the media form will likely begin to receive more mainstream attention.
Podcasts have been around for years and I feel like there is a certain element of the population who search them out and listen to them. There are thousands of different types of podcast on all kinds of subjects, and while Serial certainly engaged some people who were new to podcasts, I don't think these same people will actively search out new ones.