AM will be relevant when it moves back 2 steps and takes 3 steps forward as outlined below.
1: A realignment of the AM band not seen since the 1940's. Realign the clears for 20KHz to 30KHz spacing. Restore the AM clear channel frequencies to true clear channels (only one per frequency) and mandate power increases for clears to make them 'super power stations' with 750KW to 1MW.
2: All of the new clear channel superstations will be analog only, no IBOC, the digital portion of signal limited to transmitting Call Letters and EAS (can be done with low speed pilot tone signals). Analog stereo audio required (take your pick as the tuners will be able to automaticlly decode which method is used: Motorola C-Quam, Kahn ISB, Harris, Magnavox (which had a low-speed data option). Audio frequency response to be restored all the way out to 20KHz.
3: NTSC TV Channels 5 & 6 absorb all the AM's that are NOT clear channels as new FM stations. Note: if they remain FM analog, the existing AM/FM/TV radios will be able to pick them up on the TV portion, so the tuners are technically already out there!.
4: Most important part of the package: mandatory receiver standards. Any FM tuner must also meet AM tuner minimum reciever standards. AM tuners must have automatic noise blanking, automatic or manual bandwidth selection, minimum bandwidth of 10KHz (with better units out to 15-20KHz with bandwidth selections), automatic stereo decoding, and data decoding display (call letters / EAS).
5: FCC to strictly enforce switching power supplies interference into the AM broadcast band (LED traffic signals, dimmers, etc) in an attempt to police the noise pollution on the AM band, although the 1MW should help a bit.
AM WILL again be relevant when all these items occur, but they need to be done within the next 5 years or sooner. The clear channel superstations have a reason to run decent programming as it will cost them some money to pay for and operate their megawatt stations. The megawatt clears will also prove to be priceless during disasters and as EAS LP-1 stations as portable AM radios might be the last form of communication that works when all the chips are down. The AM superstations will compete for satellite radio listeners, and the return of music - especially on the overnights. Imagine, FREE programming - people will be surprised with the "new" AM band for the 21st century!