Is Blu-ray the end for optical storage? According to Sony, yes. The company has stated in a recent interview that the technology behind Blu-ray (And HD-DVD , for that matter) represent the technical limitations of where using lasers on optical media can go, claiming that a shorter laser isn't going to happen. They claim that for future storage needs, a new technology will have to be developed - one that will change the structure and appearance of what we expect today.
They didn't claim that current space standards are at a peak, and further improvements in technology have already been hinted at providing optical storage sizes in the hundreds of gigabytes and beyond. Nor did they claim optical storage will be disappearing anytime soon. After all, CDs are still around.
Sony didn't speculate on what sort of new technologies will succeed optical formats. When the day comes portable 50TB media is in demand, however, Sony believes it won't be an optical disc that provides it.