It's a little unclear. I found this at [URL="http://webcache.googleusercontent.com/search?q=cache:J-9EXioE0vcJ:www.elsprofessions.com/inscription/cataclysm.html+vellum+cataclysm&cd=3&hl=en&ct=clnk &gl=uk&client=firefox-a"]El's Inscription[/URL]:
Vellum now comes in one type only. The same Vellum is used for weapon and armor enchants, regardless of level. Pre-Cataclysm vellums either automatically convert directly into the new Vellum type, or become Charred Vellum. Charred Vellum is converted into the new click on use ((click it)). None of the old Vellum types will be wasted.
It's not clear from this whether we currently have 'Cataclysm Vellums' or not. I would suspect (and dearly hope) so! Charred Vellum draws a blank on google - I think they're confusing Charred Vellum with a [URL="http://www.wowhead.com/item=43146/ruined-vellum"]Ruined Vellum[/URL]. As far as I can tell, Charred Glyphs will be in Cata, but no Charred Vellum. Either way, I doubt it would hurt to stock up!