There isn't one company for internet searches and there isn't one provider for online video content. Why should there be just a handful of currencies?
The natural state of a healthy ecosystem includes competition and variety.
I only mean to say a handful will capture the vast majority of market share/cap.
Youtube and netflix are both on demand television as are amazon instant, modern cable tv subscriptions, and a variety of specific channels (hbo, showtime, etc).
There will definitely be use case dominance, but they may not be the same whales as we currently see.