And cryptos are software. So, one crypto gets an upgrade, you don't even have to sell one and by the other, soon, your coin will have it too.
Further, i expect in the future that you will be able to send whatever coins, and the vendor will be able to accept whatever coins, and the network will just automically swap them.
It may even do things like, instead of going to the vendor, to pay the wholesaler, the wholesaler will get paid in the same transaction. With post-smart-contracts.
Baby steps first. But yes, we'll be there..