Microsoft will release the final version in the second half of 2015, however you can check it out all new features on your Mac and receive regular updates as the product progress until the RTM.
Check it out at: http://products.office.com/en-us/mac/mac-preview
Written by Anderson Patricio
Anderson Patricio is a Canadian MVP in Cloud and Datacenter Management, and Office Server and Services, besides the Microsoft Award he also holds a Solutions Master (MCSM) in Exchange and several other certifications. Anderson has been contributing to the Microsoft Community with articles, tutorials, blog posts, twitter, forums and book reviews. He is a regular contributor here at ITPROCentral.com, MSExchange.org, Techgenix.com and Anderson Patricio.org (Portuguese).