FPGAs in desktop/laptop computers. That would open all kinds of interesting possibilities. Energy from nuclear fusion. Highly dense electrical energy source. I want to see electric planes, phones that last for months, drones that stay in the air for days, etc. Some kind of magical security system so we could return to native code instead of putting VMs on top of VMs. No idea if this one is feasible or how it might be…
FPGA in your desktop is a solved problem! http://www.alteraboards.com/products/ http://www.nallatech.com/solutions/fpga-cards/
Hopefully these cards will become more widespread.