If you look at the companies you have mentioned here, you will realized that they are very big players in the world of technology, their involvement in the cryptocurrency market will be one of the biggest boost for the market, just Imagine the effect of what the fund being raised by Facebook will have on the cryptocurrency market.
This step they have all taken is really a great one and I am sure that they will become a master of it, but they might never get close to becoming Master like Bitcoin. I see Facebook competing with ethereum and getting, more adopter of cryptocurrency for the market than any other project that has ever existed in the market apart from bitcoin.
They will be master in their own space I agree with you because they are already big firms but that doesnt mean that Facebook will be able to contend with Facebook in the market. Looking at ethereum is a payment system created to serve the need of people and merchants generally, so anyone can use ethereum as payment system for their product.
All these Facebook coin, Samsung coin will only be utility tokes to be used internally, that is within their system alone, which might make it a stable coin, so the volume and value needed to push ethereum away might not really be achieve, but they will fully perform well in their space.