Yes, the stations have the power - not NPR (tail wags dog). Vivian's predecessor got fired for paying too much attention to new media. She's trying to say the right things to keep her job. To placate the stations, some Morning Edition and All Things Considered stories are "blacked out" from downloading. Still she can't serve an audience wanting online access to NPR programming and the stations trying to protect their on-air turf. She will have to make a choice (with bad consequences either way).
It won't take 30 or 40 years. It's happening already. Of course, some people will hang on to OTA radio until they die (from my cold dead hands as Charlton Heston used to say). But people are switching already.
Broadcasters are already losing in the switch because app developers (the online "gatekeepers") are developing for streaming music services like Pandora and for music downloads stored in a personal library. Streaming broadcasters are getting left out.
NPR news programming is largely not bulletins or headlines - it's features, background and analysis. Like chili, it's fine the next day. Many music player users are downloading and time-shifting NPR content (getting what they want, when they want it). Tivo has been around for TV for 10 years (VCR time-shifting for about 30). The on-demand principle applies just as well to NPR. For NPR, this is a missed opportunity - and there's not really an app for that (although some users are doing work arounds with software like Replay Capture Suite).
Full disclosure: I listen to Internet radio in my car. I have a multimedia smartphone and an unlimited data plan from my cell phone carrier. My phone has a built in FM transmitter to play through my car radio. Live audio streams are subject to the same interruptions cell phone calls are and for the same reasons but I've seen great improvement over the last two years. Even so, I've gotten in the habit of downloading stories from ME, ATC and Fresh Air and "Tivoing" them to my phone/music player.
People will hang onto OTA radio, like a hard core hangs on to OTA TV (no cable, no satellite). Early adopters have already made the move. Wireless/mobile Internet technology is improving rapidly. I say critcial mass in five to ten years.