I just spoke with someone at Westone and... The housing on the W40 is plastic, not magnesium like the Adventure Series. The drivers are the same. Nothing has been tuned differently, the only potential difference in sound will be related to the new housing. So, new cable connection, and new housing, with the potential to use a cable with controls.
With that being said, I have a pair of 4r on order. Should I let it ride (seems so from the responses here and elsewhere)? The Westone rep said they switched to the new cable because the two prong design is prone to bending. I am not up to speed on these different connectors, but from what I have read here, the former Epic two prong design is more reliable?