As a long time, hard-core mmo crafter my take on crafting is this: There is two reasons for choosing a crafting profession, personal gain or profit. Each craft can be said to fit into both reasons overall, but usually for each individual character or player the crafts fall into separate reasons for use.
Personal gain is crafting for yourself. If you wear cloth you become a tailor, leather wearer does leathercrafting, ranged fighter makes guns and bows etc.
Profit is crafting items that will sell for a profit. Food buffs and weapon/gear augments are good examples.
Crafts that are generally considered personal gain crafts are Armorsmith, Leatherworker, Tailor, Weaponsmith, Huntsman, and Artificer.
Crafts that are generally considered profit crafts are Jewelcrafting and Cooking.
Once you figure out what reason you have to craft you want to figure out what kind of competition you will likely have both with others and with your own gathering efforts. Do you take weaponsmithing and armorsmith knowing full well that all the ore you gather will be split between the two? Or do you take on profession that takes ore and one profession that takes cloth. Do you think there will be a surplus of crafting materials on the auction house driving prices down or will they be scarce making you spend more time gathering than crafting or playing through the game?
Specific to GW2, are the specific upgrate materials (runes, sigils, and jewels) shared between your two professions? I guarantee those will be a serious bottleneck because they are mostly dropped items and from what I have seen they are a ton more rare than the ores and cloth and such that is basic to the crafting professions. Also what upgrades give what properties? One sigil may give power where one will give healing. More people will want power than healing on their boots/sword/whatever so expect those items to be more scarse and therefore more expensive.
Finally, are the products of your chosen craft wanted by a larger part of the player base? If so then expect more people to pick it up initially and compete with you for materials on the auction house. Expect also for the market to get saturated faster. The flip side of that is since everyone can gather, the ones who do pick up those popular crafting professions will more likely gather materials from the start and leave a higher surplus on the auction house as they get lazy or frustrated and just want to get some coin now.
My predictions for the popularity of early crafting professions from most popular (meaning more people picking them up early) to least popular is...
1. Huntsman (weapons are always a popular choice and everyone will soon see a need for ranged weapons)
2. Weaponsmith (a close second with shiny mele weapons wanted by most people)
3. Tie- Heavy Armor (only 2 professions use heavy armor, but I feel more people will use guardian and warrior)
3. Tie- Medium Armor (3 professions use medium armor)
3. Tie- Light Armor (3 professions use light Armor)
--Note-- all 3 of the armor crafts can make some form of a bag which will be highly sought after and a steady money maker for any crafter throughout the game's life.
6. Artificer (a weapons craft but not a flashy one. Many cloth users will need weapons made by this craft)
7. Jewelcrafting (accessory slots and upgrades for gear and weapons will be in high demand just not at the beginning of the game)
8. Cooking (many people will pick this up and soon drop it because of how complicated it is. expect these people to go on to something easier thinking they will come back to it later and buy their food buffs in the meantime)
I have always taken the stance that if I do what others can't or wont, then I can charge enough to make a profit. That means getting maxed first or doing crafts that the masses aren't.
Look at they guys who were the first on the server in WoW to make anything. Alchemy dragon mount? The first few who could make that thing on my server could ask a few hundred thousand gold profit over mats cost and get it until the competition ramped up.
At first glance that list screams Jewelcrafting and Cooking for profit crafts. Less people will probably take those initially and they are harder to level, especially cooking. More competition on the armors and weapons will also mean more time to profit with jewelcrafting and cooking.
My only misgivings with cooking is that I don't feel people will want to buy food buffs because other mmo's have trained us that you only need food buffs for endgame and that cooking is easy to level so they will get around to it later. I feel cooking will be a good money maker a few weeks or months after release when people figure out how hard to level this one is and how good the buffs are. I think cooking is a good choice to do as a third or fourth crafting profession either on a second character or to switch to after maxing one of your first two.
That is, of course if you are using cooking more for profit than personal gain. As a personal gain profession cooking is amazing and will earn you profit as you go along.
I personally will be picking up jewelcrafting for a primarily profit craft to get in early and fast.
As my second craft I will pick up either leatherworking or tailor depending on what my main is for primarily a personal gain craft with a chance of profit.
The added bonus with choosing jewelcrafting and leatherworking/tailor is that I won't be competing with myself over my upgrade drops and other materials between the professions. All my salvaged cloth can go to the armor craft and all my ores can go to my jewelcrafting.
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