Second Professions

So, with this new update I'm wondering if I can do all the quests and learn all the skills for each and every secondary profession. Am I reading the update wrong or can I have my cake and eat it too.

Well, maybe you need to rephrase your question a little, I'm not sure I understand it.

You have always been able to do some quests after changing secondaries in Prophecies (secondary prof quest givers at Yaks Bend, Sardelac, Serenity Temple, etc).

This update simply allows you to change to the secondaries you have unlocked (by doing desert quests after ascension or paying Senji), in any town, instead of zipping off to visit the desert or Senji again to do so.

If you are thinking you'd get skills from all unlocked professions when you complete a quest or capture an elite from any profession then no, it is just like it has always been, only those for your current 2 professions.