The key here is if the DEV and PROD WSDLs are the same.
If they deployed their WSDL without changes from DEV to PROD, then you don't need to regenerate your classes, I am pretty sure.
So you can just point your code to the PROD endpoint.
But if the PROD WSDL is different from the one in DEV (which should not be the case normally once they did a DEV to PROD release of their WSDL), then you will need to regenerate your client-side classes.
Basically if the one managing the WS changes something significant (e.g. adds parameter somewhere) in their PROD environment you also need to change client code in your PROD environment (for the two systems to stay in sync).
That's what I know based on my experience.
Hope it helps.