All that is missing is some cross-chain integration / middleware between some of the main chains. Whaleshares and BTS have it already but I'm not aware of any EOS integration with them to date.

This is starting to happen now though on other chains and projects. Have a look at what Bancor is doing for token exchange between ETH and EOS. In time I can see all the main chains kind of "meshed" together in some way.