If Bekele is close to his best, than nothing Rupp can do will beat him. It won't matter if Rupp goes from the gun, from 2.5k or from 4k, Bekele will beat him. But we don't know what Bekele has right now. I agree that off a slow (13:20) or medium (13:10) pace Rupp going from 1000 would be as good a strategy as any to throw at Bekele.
The thing is, this will not be a 13:20 or 13:10 race, it is a loaded field that will have pacers taking it at sub-13 pace, with 7 or 8 guys who are as good or better than Rupp. If Rupp goes with a 1000 left in this race he may well finish 8th.
In a race of this quality you need to be flexible and have 3-4 plans for different contingencies based on how the race plays out. And you need to stay aware and thinking.