TDK recently developed a 1000GB (aye one terabyte) Blu-ray disc, that a lot of existing recorders can record to with only firmware upgrade.
Its still in prototype stages, but its something that will be interesting for the future.
Personally I will probably just buy a PS3 for Blu-ray, but it wont be any time soon, probably when DVD's finally become obsolete. I dont need HD.
Blu-ray on PC's is the thing that it will benefit most, for backing up data.