We had a chance to see DDR2 8GB modules from Samsung in RDIMM format and we are very sure that this memory is for servers only.
It was still cool to see 8GB in a single module as this would bring amazing 32 GB in four modules on an average desktop board. Most of Intel boards are limited to 8GB total memory due to an addressing issue and 4x2GB is the best case scenario.
Maybe the future brings 4x8GB at some
point but I am sure that this won't happen that soon.