We now have some very viable units in mass production at reasonable prices. I understand your scepticism, but I do not see 3 years as being overly optimistic. Right now it would be quite possible to illuminate your entire house (including garden floodlights) with commercially available LED lighting.
Personally I would fit about 20 or so small flush-fitting 5W LED units into the ceiling of a medium size room. It would provide an
*extremely* bright but glare-free room (when needed) and an even, shadow-free light. Dimming can be achieved by not having them all switched on, which also has the advantage of allowing part of the room to be bright (perhaps for reading) and another part dim (for TV viewing).No, efficient LEDs that are bright and efficient have been in commercial production for a couple of years now, and the prices have fallen to economically viable levels (still relatively expensive but dropping fast).
It will be necessary to replace the light fittings for the foreseeable future, yes. Not a huge undertaking, but not trivial either. The more directional quality means that light placement is more critical, and as said, plan on using a spread of several units to replace a single tungston/CFL unit. I would recommend that anyone planning to redecorate a room should look into fitting LED lighting as part of the redecoration. I can almost guarantee that you will be pleased with the result.
Yup - but don't use future tense. It's already been done and is available to you right now. Unfortunately there are some really crap designs and also unrealistic claims together with the good stuff, and buying a badly designed product is likely to make a person dismiss the technology as being inadequate. Price is not necessarily a good guide.
Metal halide are not as efficient or long-lasting as LED. And whilst metal halide is a mature technology where incremental improvements are relatively small and infrequent, LEDs will improve in both quality and price quite rapidly as the market grows.