MW will offer pseudo privacy as before this history gets deleted those monitoring the network will be able to store the chain state, meaning even if values are hidden it is still possible to track user activity and interactions, so while yes, this will help with fungibility it is by no means perfect.
TL;DR: Mimblewimble’s privacy is fundamentally flawed. Using only $60/week of AWS spend, I was able to uncover the exact addresses of senders and recipients for 96% Grin transactions in real time.