Hello,
No I don't think that's really related because
If you are currently using undefined/non-standard URLs (SOAP) for the services, please check your URLs prior to January 2018 to ensure your services with FedEx continue and will not be interrupted. See below the corresponding URLs for the impacted FedEx Web Services WSDLs.
So I don't think they closed down the "old" URL and if it was the case, I think that we would have a lot of feedback on it.
But, it is sure that it would be good to get the new WSDL file before January 2018.
Right now, I really recommend you to contact your web hosting in order to see what is the issue for contacting the fedex server.
Because, even if the URL will migrate in the future, the "could not connect to host" cannot be related since the domain "fedex.com" still exist and won't disappear ! So if it was really the fact that the services are not more on the fedex.com server, you would have another error message giving you an incorrect server answer, not a "could not connect to host".
Regards,