I am not getting into the Li-Fi game, but I would like to throw in my 2 cents for my fellow domainers as advice. I work with technology every day and I hate to see anybody "waste" their money.
Li-fi is great technology but like many have said before.. its still in its infancy. It is fast, secure and has great potential, however I think the limitations should be considered before investing into any technology. The main problem with Li-Fi is that light cannot penetrate solid objects which means that the uses for it are limited to a specific spot. Can it still turn into great technology? Yes, however I would recommend that you concentrate on smaller area keywords to go along with it (receiver, bulb, hotspot etc).
Also, before anybody tries to argue that it might develop into something bigger technology wise and how well it can be integrated.. I am not saying that it can't be, however current technology shows that Comfort / Price will be chosen over Speed. We're already using light to transmit data.. its called Fiber optics.
Is fiber optics technology used? Sure but currently mostly for businesses because its expensive
Is it faster than WiFi? Sure but currently its expensive while a wireless router cost $20
Is it more secure than WiFi? Sure but its still expensive
Again, I am not trying to be a downer.. Invest in whatever domain you want to buy but maybe consider my thoughts before you hit the purchase button.