Announced on October 25, 2016 on the Power BI blog, they are releasing it into technical preview. For this first review, you'll need an Azure account. No mention of when a local, on-premises preview will be available, but still this is great news.
See: Technical Preview of Power BI reports in SQL Server Reporting Services
Video - here's a video showing Power BI against SSRS 2016
Create a modern enterprise reporting and mobile BI solution with SQL Server 2016
Can I try it out on-premises?
Ok, what you really want is to run a localized VM version. Christopher Finlan has added a posting that outlines how you can download the VM from Azure and get it up and running as a localized VM. Find that post here: How to run the Technical Preview of Power BI Reports in SQL Server Reporting Services on-prem using Hyper-V