Siebel and Middlware WSDL definition and optional attributes

Hello -

Siebel consumed web service published by our Middleware system. We imported MW wsdl and created external IO.  After that we’re converting External IO into an internal IO and using Siebel EAI adaptor for an Upsert operation.

The same Middleware service is consumed by other systems in addition to Siebel. (e.g. PeopleSoft, Taxware etc.)

Now Middleware team is adding an optional field in the web service to support peoplesoft requirements which we’re (Siebel) not interested. 

Does Siebel need to update External IO with new field(re-consume Middleware WSDL)?  i.e add new field in Siebel external IO that MW is adding even if its optional.