before much longer drive letters will be irrelevant, and data will simply be accessed via a storage database which will allocate locations depending on file type / size etc
When we have universal internet connectivity and permanently accessible cloud storage, the actual data location won't matter to you. - whether its held locally or remotely. As long as you can search the database list of files and find what you want, thats all that matters
The Microsoft Search utility was intended as a first step down this route, but got stagnated when M$ pulled back on using their new file system in Vista