I very much doubt they will drop by a substantial amount, they may even go up. Remember, the only way we can harvest these at the mo is via the casio projectors. The price of the projectors would have to drop a lot to get the diode prices down. I believe its possible that casio may develope a way to stop us harvesting the diodes from future projectors - If that happens the prices will sky rocket again unless we can find out who supplies casio with the diodes in the first place. My guess is that either casio make these diodes themselves, or the contract from said possible supplier to casio, is solely to casio.
Even if such a contract existed and we found out who supplies the diodes to casio i very much doubt anyone would be able to afford the minimum order cos they'd probably be in 10's of thousands. An order of 1000 diodes would only make around 400 projectors for casio, thats a tiny amount if you look into how many they must have sold worldwide.