Just in case you were hoping that due to Inscription or any other of the huge profession changes coming in Wrath of the Lich King, you'd get another expansion slot, Bornakk confirms that you will not -- despite all the changes to professions, the way that characters choose them will not change.
But Kevin G (who kindly sent us this tip -- thanks!) brings up another interesting profession topic -- just how are Death Knights going to deal with leveling up their professions? Surely, since Blizzard doesn't want them running around level 1 areas like noobs, they wouldn't actually have to level up from the beginning, would they? As hilarious as the thought of a black armorclad bringer of devastation chasing wolves around Elwynn for their leather is, it's probably a good bet that Blizzard will avoid that scenario.
But how? We have no idea yet. We do know that Blizzard wants to make things easier for people leveling professions all the way up (especially from the higher levels), so maybe there'll be a plan in place that Death Knights can get in on (maybe a quest to do, or a simple charge of a few hundred gold, since that's probably what it would cost to just buy the lower level stuff off the AH). Either way, hopefully we'll see a solution that's both easy on Death Knights and fair to characters who've leveled it up the hard way.