From the recent news, only the AMD Fury will actually use HBM. The 3xx series are going to be "technically" rebrands of the 2xx models; however, while they'll still be using GDDR5 VRAM, they'll have slightly tweaked clocks & a lot more VRAM (IIR, the 3xx equivalent of the R9 290 will have 8GB of VRAM).
Still will probably be good deals, but just wait a week until they're released.