Spotted by a member of 3D Center forums, the two LinkedIn profiles mention both the R9 380X by name as well as describe it as the world's firts 300W 2.5D discrete GPU SoC using stacked die High-Bandwidth Memory and silicon interposer. While the source of the leak is quite strange, these are more reliable than just rumors.
The first in line is the profile of Ilana Shternshain, an ASIC Physical Design Engineer, which has been behind the Playstation 4 SoC, Radeon R9 290X and R9 380X, which is described as the "largest in 'King of the hill' line of products."
The second LinkedIn profile is the one from AMD's System Architect Manager, Linglan Zhang, which was involved in developing "the world’s first 300W 2.5D discrete GPU SOC using stacked die High Bandwidth Memory and silicon interposer."
Earlier rumors suggest that AMD might launch the new graphics cards early this year as the company is under heavy pressure from Nvidia's recently released, as well as the upcoming, Maxwell-based graphics cards.