Stealth,
I would say 2 years would be tops, hopefully even sometime next year. I think the next generation of LEDs will probably do the trick. I think it is very close at this time.

Regarding distance and lenses: There is a trade off. If you are doing vertical plants, you need all the penetration you can get Then you need the lenses to really get the light focused. . However you give up covering a wider area and a take a 15% energy loss. At this time I am leaning towards the horizontal grow and very close lights evenly distributed. But who knows. It is really still experimental. That is why it is good to be exchanging info and results.