The new experience system won't require skill development to level in any class. Though skill development will definitely assist you as it'll provide an alternate (or supplemental) source of class XP as well as bolstering your ability to use those skills with better proficiency.
Professions are another matter and WILL require skill development in certain areas. More on them later, since they are not going to be released with the rebuild.
Skills will be more difficult to learn than before as some people have 'maxed out' certain skills after only a month or two. Also, they'll grant a far smaller bonus to combat than previously (since the skills aren't necessary to excel in a class).
Developing skills will:
- Allow you to progress in a profession
- Award you some regular XP
- Allow you to earn special mastery titles
- Allow you to accomplish certain tasks better (such as crafting a certain type of weapon)
- Allow you to teach skills to other characters
- Give you some bonuses to using those skills in combat (not as much as before, but to a noticable degree)
- Allow you access to certain spells and abilities
- and more...
- Grant large combat bonuses
- Grant a lot of regular XP
- Help you make strawberry smoothies
If you are an excessive user of skills (such as non-combatant characters), you will find that you may gain sufficient XP through skills to level normally up until a certain point. Then it becomes hard to rely solely on skills. That's where professions will step in and lend a hand as an alternate experience system. Professions are not ready yet, but they lay in waiting just around the corner...