Bluray will last as long as th industry dont find a purpose where Blurays are to small.
Because aslong as you cant offer a good way to use the new media noone will buy it.
And bluray can have capacitys up to hundreds of gigabyte with dozends of layers.
Bluray will be improved in the future. And I dont see good reasons to have a new media. Atleast the next decade. I have a feeling that Bluray will last pretty long. Sony has no reason to force another type of discs in peoples living rooms. Bluray will probably last way longer then DVD or CD. I dont know if new technologys like a new type of 3d will require TBs of Data but aslong as the technology dont need more then 500gb-600gb (20 layer). We definetly wont see a new technology.