There may not be one single dominant blockchain network in the future, thus, will blockchain start to interoperate in 2018 
It is likely blockchain starts to inter-operate next year because 2018 will be the year when major financial institutions will adopt digital assets, and marks the birth of hybrid blockchains.
To make the broad use of digital assets truly mainstream, however, I think we’ll need the many blockchain networks that currently exist to inter-operate. The truth is there will not be one single dominant blockchain network in the future as there isn’t any dominant internet or email provider globally today. Looking at the use of email address which is being inter-operated that is we can all email family, friends and colleagues from Gmail to Yahoo to Outlook seamlessly and instantly. Likewise, value should move across all ledgers in exactly the same way irrespective of the blockchain network, PayPal wallet or traditional bank account involved.
https://www.coindesk.com/death-ico-4-2018-predictions/
