There has been some discussion in the official WoW forums about the limited attempts and how to get to the Lich King in Icecrown Citadel. Blizzard had the following to say about the rationale around limiting tries and what you can access before getting to the Lich King. It also clarifies that you will be able to access each of the new wings even if you have not defeated one of the other wings, as long as you have gained access to the upper spire.

Limited attempts in Icecrown Citadel

The purpose of the limited attempts is to really challenge players and we felt that was a really important aspect of Icecrown Citadel as the grand finale to the story of Wrath of the Lich King. We know that a lot of players want to get access to everything and defeat it the second it's released, but having a system like this helps provide additional challenges and for those who may not be able to overcome them, things will get easier over time through additional attempts, better gear, and eventually the buff.

Since it also relates to difficulty, I wanted to mention that you will not be required to clear the Plagueworks before entering the Crimson Hall or the Frostwing Halls. Each wing is independent and you are free to explore them in the order of your choice once they are open.

In order to be deemed worthy to face the Lich King however, all three of these wings must be cleared. In addition, Professor Putricide, Blood Queen Lana'thel, and Sindragosa must also be defeated on heroic to face the Lich King on heroic mode.

Challenges await, so good luck!