Well, Sony's second-gen players will arrive this summer, and that should herald the beginning of onboard decoding capability across the board. (That player will cost $600, and I saw a comment recently that Sony was theorizing that entry-level Blu-ray players will drop to $300 by this December). The Blu-ray Association has also recently mandated that all players sold after some time in October provide full support for BD-Java (the interactive layer). That transition is going to make it much more reasonable to provide discs that use the new formats instead of PCM.
As for when PCM will start to disappear from new releases, I would say that it's already happening. PCM will
always be allowed by the Blu-ray spec, but it has
never been required - it was done initially because it was easier to master for when using the format's brand new mastering software and because it was guaranteed to be compatible with the first players. The "bit budget" burden of using uncompressed multichannel PCM is significant, especially when studios would like to use single-layer Blu-ray discs when possible (dual-layer was difficult to get into production and still comes at a cost premium). Studios are already beginning to use DTS-HD (which includes a traditional DTS bitstream that works while we wait for somebody to get a DTS-HD decoder to market) and even old-fashioned Dolby Digital on new releases more often than PCM. Take a look at
this batch of recent HD disc reviews at Secrets: of nine Blu-ray discs, only two contained PCM soundtracks. Other batches fared a bit better (
4 of 9 and
6 of 10 , although one of those six was a music title - something that will always be a candidate for PCM), but the trend has already begun and will likely continue as the year goes on.