I understand that they sold purchasable skills in the original Guild Wars, I have it. I'm just wondering, is it a for sure thing that they will do the same for GW2? They release skills to the public on the profession reveals, but those can't be the only ones in game, can they?!?
First, in Guild Wars 1 you could indeed buy "skill unlock" packs, but they just made life easier on those people wanting to play pvp by offering them all the skills available in the game right from the very start... they didn't give you any skills that could not be found in-game by normal playing.
The same will apply to Guild Wars 2: they will definitely not sell skill packs with skills that are not already in the game and can be obtained by normal gameplay, as they said they would never sell power advantages in their store.
And as people playing competitive pvp will get immediate access to all the profession skills available in the game, there is no need for such skill unlock packs in GW2 anyway. So in short... skill packs for sale for Guild Wars 2? I sincerely doubt it.
As for skills outside of your profession... yes, definitely. First, the set of profession skills that are known now, is only a very small subset of the actual profession skills for each profession that will be in the game. Only the first five skills, those based on your weapon, are fixed... there will be a lot of skills to choose from for your second set of five (healing/utility/elite) skills. Plus, by means of the trait system a lot of customization of your skills is possible. Also, there will be lots of environmental objects that you can pick up, and which will then change your first five (weapon) skills... offering you quite a bit of variety for those skills as well.