You can buy Plasma lights already, LG do one, it's 719ukp though for a 730w one. I will probably doing a test grow with one later this year.
You can buy them here:
The price has fallen 30ukp in 3 months, hope they continue to get cheaper!
Plasma lights are not complicated at all, it's just a glass envelope full of exotic gases with a cavity magnetron (same as you have in a microwave oven) on one end, the microwaves it produces excite the plasma causing light emission. The spectrum of this LG light is 6000K, far too cool to be ideal for flowering, but good for veg. The big issue I see with it is the 120 degree beam angle, which isn't very good light distribution.