This weekend we did a migration between 2 tenant and with this migration we noticed that the URL for OneDrive 4 Business was changed on the old tenant after we changed the domain name for all the users.
This means when you change the UPN of a user not only the primary email address is changed but also the user profile in SharePoint Online.
I did a test with another tenant to see how long it takes for the URL to change; this gives an indication about the profile update time.
The email address is pushed in about 5 minutes to your SharePoint Profile and the URL is changed in about 30 minutes.
Before the URL change
After the URL change