This is absurd. In order to be a world-record-holder you have to be ridiculously talented, even relative to world elite, before the doping. So if no one runs 12:37 for you, you don't have any new information, other than that the next big talent has not yet arrived.
Besides, Kenenisa Bekele is way less suspicious than the Chinese women who hold world records. So even if this COULD work, I'd much rather see $1 million aimed at, say, the women's 10,000m world record.
BUT HERE'S A WAY, WAY, WAY BETTER IDEA: Aim the money at regularly running a distance that is seldomly run. You could perhaps have another quality 10,000m race every year, which is lacking across the world. Or you could run the two-mile twice more per year, so that you would be able to build up a better data-set of how strong 8:03, 8:07, etc. really is relative to runners of the contemporary era.
Or, you could run your 5,000 but give time-prizes, like sub-12:50, so people could get the fast 5,000 that they crave every year (although Kejelcha's recent 12:53 was quite nice!).