The latest device ID added to RadeonSI was 0x6995. This now brings it up to seven Polaris 12 IDs in the open-source driver. As always, it doesn't necessarily mean there will be seven different "Polaris 12" graphics cards AMD is launching but some of these IDs are simply reserved, etc. For reference there were nine device IDs for Polaris 11 and 11 for Polaris 10.
We spotted Polaris 12 back in December when the patches emerged for adding this support. The code isn't doesn't change/add much over Polaris 10/11.
There's some speculation that Polaris 12 may premiere in the Radeon RX 500 series, or at least in part, and those GPUs will be launching in April. The RX 500 series is not the upcoming Radeon RX Vega GPUs that will be launching likely at the end of May. With Polaris 12 / RX 500, it's likely just higher clock-speeds and a re-branding. The PCI IDs that have been mentioned in the recent AMD Radeon Software Windows update also reveal some of the RX 500 hardware still align to Polaris 10/11, at least compared to the Linux driver PCI ID lists.
The Polaris Refresh may not be as exciting as Vega, but at least there will be good open-source driver support at launch as with Vega we haven't yet seen any of the actual hardware enablement patches (hopefully in time for Linux 4.12 and Mesa 17.2) and it's likely to require AMDGPU DC/DAL support.