A news article from the BBC outlines work by a team who are developing an improvement to LED streetlamp designs, which they claim will be able to reduce the wasted light (i.e. that which goes in undesired directions such as ‘up’) to just 2%.
Assuming that the design (which is still theoretical, to be prototyped in October 2013) works, and that local authorities actually replace wasteful and light-polluting streetlamps with the new hardware, it will be still be some time before enough have been swapped out to make a positive difference to the night sky. Many areas have not switched to LEDs at all, with a large number still using low-pressure Sodium (old-style, very orange) and high-pressure Sodium (newer, yellow-white) bulbs, while others such as Knowsley have been implementing Philips Cosmopolis White (metal-halide) lighting.
Of course, one major issue regarding astronomy, light-pollution and LED lighting is filtering – it’s much easier to filter out truly monochromatic light (as in the case of Sodium vapour lamps) than it is with broad-spectrum LEDs. If, however, the light does not flood the sky in the first place, the problem may be less of an issue than is feared.
Let’s hope the future is, in terms of the night sky, dark rather than bright!