We use this setup a lot. I just did this a few months ago at a clients office. We will be migrating again this month. Because of the nature of PST's (they almost always grow) it is helpful to plan for another move in the future.
First, before making any changes, be sure you have a good backup of all data.
Assuming all of your foaming profiles are in a single location setup DFS to point to your profiles folder.
ie \mydomain.local\files\profiles goes to the directory where the profiles.
For this example I will assume that each users profile is located in a directory that is the same as the username (%username%).
Change all users profile location to \mydomain.local\file\profiles\%username% in ADU&C
What this does is allows you to change the location without changing the location listed in each user's properties.
Verify that there is no issues at this point and everyone accesses their profiles.
One night after hours when no one is logged in (after verifying you have a good backup), copy the files to the new server using robocopy (drag and drop can cause problems), and re-point the DFS share.
In the future all you will have to do is the last steps. I highly recommend DFS as it makes any kind of data move much less painful.