We are working to support the upcoming API changes around the new marketoGUID field announced at http://developers.marketo.com/blog/important-change-activity-records-marketo-apis/ . I have a question regarding WSDL versions.
If I login to Marketo and go to Admin -> Integration -> Web Services I can see our SOAP endpoint URL, including version.
From my testing, it appears that simply replacing the version show in the admin dashboard works, but I'd like to know if there are any other considerations to take into account.
If you see a new version in Admin, still you can use the old version endpoint, but if you want to use any new functionality introduced in the new version, then you have to change the endpoint.
PS: Avoid using SOAP for connecting with Marketo, as nothing new will be introduced in SOAP. Shift to REST API asap.