1) Could Haile or anybody else run the marathon in under 2 hours at the 2012 Olympics?
A: Certainly not. 1 - no athlete on the planet is remotely close to pulling off that right now — especially in a summer marathon sans a pace- setting rabbit. 2 - Olympic marathons are tactical races for national pride, rather than individual time trials.
2) Is it physically possible to run a marathon under 2 hours?
A: Yes, I think so as more time goes by. Bear in mind that in 1997 the 1-hour mark was finally broken in the half-marathon. Over the past 13 years that WR has been lowered a mere 90 seconds. So the progression to a sub-2 will require quite a few more years.