I'm looking at the professions for WotLK, and what they offer, and I have to say Leatherworking may not be the only good thing...
Skinning will give 25 crit rating (which is nice) and leatherworkers can make their own armor. Armor kits for LW are cheaper, but there are no BoP armor kits that are BETTER yet, so for a leatherworker it comes down to the gear (which is not in beta yet).
Mining will give 64 AP and 35 stamina (much bigger bonus than 25 crit). Engineers will be able to make goggles (which are always cool) as well as some cool gadgets. Jewelcrafters will be able to make their own BoP gems which are slightly better than the BoE versions as well as their own trinkets. Blacksmiths will be able to make their own weapons and socket gear! More sockets to your gear than to other players (e.g. you can socket anyone's belt and weapon, but only your bracers and gloves).
Herbalists get a HoT on a 5-min cooldown (not much use for a hunter). Alchemists get bigger bonuses from their potions, but IMO not that big a bonus (compared to an extra socket).
Inscriptions get an extra glyph, although what type of glyph remains to be seen.
My opinion is that mining+blacksmithing is going to be a powerful tool. You miss out on some of the pieces of gear that leatherworkers make, but on a BoP set that consists of chest, bracers, and belt (which usually sets like that consist of) you're not missing out on too many stats except for the chest-piece, and a weapon has those stats. Not to mention that mining > skinning.