Microsoft's product development never stops. Even before a major version is released, developers are already thinking about what will be included in the next revision.
Over the weekend, Microsoft began offering the Office Pre-Release Programs sign-ups. Using the link below, you can submit your name, address, and a few details about your current computing environment and be entered to be considered for a spot in a future Microsoft Office Pre-Release program (read: Beta).
Most interesting during the sign-up, you'll be asked for a Google account, Apple ID, and whether or not you use social media. This is a U-turn from past offerings, showing that Microsoft is dedicated to providing Microsoft Office on all major platforms like iOS, Android, and Windows.
Go here to sign-up and be considered: Office Pre-Release Programs
Remember, beta software is software that is not complete, could contain bugs, and hamper your computing experience. A program like this is less about complaining, and more about providing honest, constructive feedback. If you're not ready for that, don't sign up.
A good example is the last week's late release of the Lockscreen app from Microsoft for Windows Phone 8.1. The release was ho-hum and extremely buggy. This resulted in complaint after complaint while it was clearly identified as beta software.