I believe in the future no only one but between 4-5 coins exist. Every coin has its own niche.
But most altcoins will fail longterm.
I agree on your first statement with regards to actual blockchains and pure coins. I think tokens with their own apps that link to the real world can be plentiful and very diverse in their utility. This is where every niche products will come in to play and I can easily see there being dozens of successful apps linked to tokens that operate on the blockchain.