The number of coins will probably be reduced to only essential projects that will be fully integrated into our day-to-day life. In order t be succesfull, these coins will have to be interchangeable between blockchains, this can be done by implementing sidechains that connect with each other to allow for interoperability.
So true! If there will be lots of coins, I think the usability of each coin decreases since there are lots of choices. The investors will invest different coins therefore lesser demands for each of the crypto coins. Where as if there is few coins to choose bigger will be the demand dor each.