Meh, I think that filenames are too limiting these days. Meta data is where it is at. BeOS had metadata. I think MacOS X is getting it in the next release.
Instead of the filesystem just having an entry for the filename, and the OS either having to decipher the type from the filename, or from the file itself, the filesystem would provide type information itself.
instead of: CompanyAccounts.xls
You'd have:
Displayed Name: Company Accounts
Type: Excel File
Creator: Billy Bob Thornton
Project: Company
and the other things like creation date, updated date, etc that already exist
MP3s could store all the metadata in the filesystem, instead of in a wrapper on the file, for example.
Amiga could do this with the .info files, as that could handle things like that.