We are in the point of a cambrian explosion right now. Only the winners, aka the ones that bring value and utility, will survive over time.

I don't' think that we need a specific number, low or high. Bitcoin as slow as it is, it's very good for the store of value. A faster coin like Ark or Neo is good for currency because of faster transactions and easy to use API.
I think for now we are stuck with one coin for one purpose. It's hard from a technical point of view to develop a universal platform for all use cases. And it's become more centralised over time.
A very fast exchange is what we need at this point.