There are a lot of changes to professions in the new expansion, so I made this page to list what I gathered so far. I will update this page everytime I find something interesting in the new beta builds. Last update: november 1.

General changes

• Direct combat benefits of Professions will be removed. This means you no longer have to level professions to get 0.5% dps increase, so leveling a profession will be more like a personal choice now.
• Realm First profession achievements are gone.
• Work orders and profession daily cooldowns convert raw materials like herbs and ores to a more useful reagent. Almost every new item you can craft requires this reagent generated from doing work orders, or your profession daily cooldwon, these reagents binds on pickup.
• You can craft items at your garrison without having professions. But, you can't craft the best items, consumables.
• Herbalism, Mining and Skinning will be easier to level. You can now pick herbs, harvest mineral nodes and skin animals without a required skill. The amount of ore/herb/leather you'll get is determined by your skill level. This is similar what we have now for herbs and ores in pandaria. You can read more about this here.

There is an event called Darkmoon Faire that appears in the game once a month, starting at 00:01 on the Sunday before the 1st Monday of each month. During the event you can complete quests for each professions.

The profession quests can only be completed once during each Darkmoon Faire and will grant 5 skill points (means you can complete them again once at the next faire). 

The skillups will apply automatically to the most recent expansion profession progress that is not at its maximum. So, for example, if you want the +5 skill in Outland Engineering, but you have already learned other expansions profession skills, you have to max all of them out first, then you can get the +5 in Outland Engineering since that will be the only one that is not at its maximum.

I know that most of the players who will try to get the Realm First! Illustrious Miner achievement are beta players. For those of you who weren't lucky enough to get a beta key, I made a guide which can help you to get this achievement. The mining routes on the maps are also the best routes to farm the ores on the first day when Cataclysm launches. First, you need to have a mining skill of 450, that's pretty obvious for everyone I guess. It's also important to have the following enchant: [Formula: Enchant Gloves - Advanced Mining]. You need the enchant because you can leave Mount Hyal earlier this way at 470, and you will be able to mine Pyrite Deposit at 520 and Rich Elementium Vein at 495.