With the Halo 5: Guardians Multiplayer Beta launching in a few hours, Xbox have announced the special editions and pre-order bonuses for the full retail version of Halo 5: Guardians which releases in Fall 2015.

Standard Edition for $59.99 – Halo 5: Guardians plus an exclusive poster, only available to those who pre-order.
Limited Edition for $99.99 – Everything in the Standard Edition plus new digital content to enhance Spartan combat and exclusive items wrapped in a uniquely designed steel book.
Limited Collector’s Edition for $249.99 – Everything in the Limited Edition as well as additional content such as a commemorative numbered statue designed by 343 Industries. More details on the design to be shared at a later date.
 
The article from Xbox Wire also gives us a small snippet of new information about the Halo 5: Guardians story and what ultimately leads Agent Locke to start hunting for the Master Chief:

Peace is shattered when colony worlds are unexpectedly attacked.  And when humanity’s greatest hero goes missing, Spartan Locke is tasked with hunting the Master Chief and solving a mystery that threatens the entire galaxy.

Colony worlds have suddenly been attacked and Agent Locke is tasked with finding the Master Chief to solve a mystery that is threatening the entire galaxy. Could this new threat be the ones attacking the colony worlds? Hopefully we learn more in the near future.