The Miscellaneous Class is intended as an interim stage prior to a breed becoming eligible to compete in a variety group at AKC shows. Under our current policy, dogs would become eligible for registration at the time that the breed is brought into the Miscellaneous Class.
Before entry into the Miscellaneous Class, the Board will work with the national club to determine the variety group to which the breed will be assigned. After a limited time in the Miscellaneous Class a date would be set, at which time the breed would become eligible to compete in a variety group at all-breed dog shows.
This information from the AKC Recognized Dog Breeds web page
The AKC Board of Directors has the authority to add a breed to the list of AKC-registrable breeds if, in its opinion, sufficient evidence is presented to justify such action. There are a number of factors the Board considers in making this decision, including documentation that the breed in question has been breeding true for many generations, with accurate record keeping; evidence that there is sufficient interest in the breed throughout the United States; and a national club in place that meets AKC requirements to act as the parent club for the breed.