The one winning horse you will have backed will be offset by all the losing ones.
Fact is the sum of all preorders and upcoming orders (far) exceeds the mining profit thats to be had. Buying equally from all suppliers just guarantees you get an average result, which is negative.

The only way for your strategy to work is if most companies do send out early orders in a mostly timely fashion, but subsequently struggle to produce and ship their long order queues, like BFL has been struggling for years now.
Its possible, but I wouldnt bet on most/all of them being equally inept managing a supply chain.