Blue Post, http://us.battle.net/wow/en/blog/1191652
“As you’re all aware by now, the shattering of Azeroth will drastically and permanently alter the continents of Kalimdor and the Eastern Kingdoms. In the wake of Deathwing’s devastation, adventurers will be summoned to embark on new quests from levels 1 to 60 in these transformed territories — and with so much new content to be found on these original two continents, many original quests will no longer be available after the shattering occurs. These quests will automatically be removed from your quest log, while any quests you’ve accepted that still exist in Azeroth will remain in your log.
You may be wondering how the shattering will affect the Loremaster achievements. If you’ve already completed Loremaster of Eastern Kingdoms or Loremaster of Kalimdor, you will not lose your achievements. However, if you’ve made progress toward these achievements without yet completing them, be aware that any quests that are removed from the game will no longer count toward your progress, so you may see your achievement quest counter drop. If you’re close to earning either of these achievements, we strongly suggest you finish them with great haste, as Deathwing’s return is imminent.
In addition, the Loremaster achievements are being redesigned slightly to make them easier to track. Rather than having players complete a huge number of quests throughout a single continent, the criteria will change so that you will instead need to complete a set number of quests in each zone. Once you’ve earned the achievements for each listed zone on a continent, you will then be awarded the Loremaster achievement for that continent. For those who do have Loremaster of Kalimdor or Eastern Kingdoms completed already, you can still go back and get the new achievements for questing in individual zones on those continents.
We look forward to giving you an opportunity to take on brand new adventures in these classic zones. The times they are a-changin’.”
If you are working on this, I highly recommend the mod Everyquest. It can ping the server and find the quests you have finished and what you’ve left to do. Its a great tool for finding the zones and quests you still need.