During a presentation is Zaragoza Spain, Sony representatives confirmed that all future Sony Alpha cameras will have translucent mirror technology (see also pellicle mirror).
Recently Nikon and Olympus have filed patents for similar translucent mirror implementation. I personally believe that Sony is taking a huge risk with this translucent mirror technology - Canon tried that back in the 1960s and abandon it:
"However the novel design has its flaws, the obvious ones being loss of light, which after all is not very significant; one third of a stop loss in the exposure, that amount being redirected to the finder, which is two thirds of a stop dimmer compared to using a fully reflecting mirror. A more serious problem proved to be that the image forming light rays has to pass through the stationary pellicle mirror. Over the time, the mirror surfaces become soiled; it scatters the rays and degrades the recorded image. The finder does not go black, but at small apertures, the eye has no time to adjust to the dark finder."
