Speculation: there would normally be a Release Candidate, or two, shortly before final release. But since LR4 is really a database wrapper around a new version of Camera Raw, which will, presumably, be released with CS6, I would imagine that LR4 will not be released before CS6 is ready. That time is, obviously, getting closer, judging by the sneak previews, but whether it is 1 week, or 1 month or one quarter, only Adobe will know, and perhaps not even they. If I was them, I would wait until the slew of new Nikon, Canon, Fuji, and other cameras that are due to be released over the next month or two were handled by ACR7, if they want to avoid a lot of negative internet vibe about a new product not working with new gear.