Nothing about the latest release requires you to make any changes to your skin. We have had a system that allows the css files to be organized any way you like since version 2.2.7.7, so as long as you are not upgrading from a version older than that there are no changes required.

All we've done is organize the css files differently in the included skins to make things easier for designers to find. We combined some files and renamed some files but the css itself did not change, just the file organization. The style.config file is what determines which files are included. Your custom skin will keep working as it does, there is no need for you to re-organize the files in your skin the same as the included skins. 

Best,

Joe