Is equanimity (upekkhā ) the highest Divine Abodes (brahmavihāra)?

Brahmavihāra; the four sublime or divine abodes, also called the four boundless states, and the immeasurable deliverance of mind; are 

• mettā (loving-kindness), 
• karunā (compassion), 
• muditā: (altruistic or sympathetic joy) and 
• upekkhā (equanimity).  

Each of the four brahmavihāra are practiced simultaneously and one is not more or less important than the other.  It is not possible to practice one brahmavihāra without practicing the other three. 

Equanimity is the attitude of detached impartiality towards beings and is not apathy or indifference.  The mind that is free of attachment or clinging is impartial towards beings, does not value one over the other, and radiates loving-kindness, compassion and sympathetic joy.

Please keep in mind that the teachings of the Buddha was first memorized before they were written down hundreds of years after the parinibbāna (physical death of the Buddha).  The teachings were organized in order to aid the memorization and lists were established.  In many instances the lists of items of a teaching are not meant to convey that the items are practiced one after the other.  By investigating the list of items you will discover that it is impossible to practice one item without also practicing the other items as well.