According to sources who wish to remain unnamed, we should see an AMD Tonga XT-based graphics card launched sometime in September.
Our sources report that AMD is indeed planning to introduce an XT version of the Tonga GPU which will not only have a higher Stream Processor count, most likely 2048, but also come with a wider 384-bit memory interface. While no names were mentioned, we would not be surprised to see the R9 285X in September. The Radeon R9 285 is coming a few week ahead of the R9 285X and we should see it by the end of August.
The most surprising piece of information is the wider memory interface, which means that the R9 285X will pack 3GB of GDDR5 memory.
Our sources suggested that some AMD AIB partners already have samples of the new card and are tweaking clocks and designs.
The new Tonga XT-based graphics card should end up faster than both the Tahiti XT-based R9 280X and the GTX 770 while drawing less power, which suggests that this should be a very good piece of hardware in terms of performance per watt.
Of course, as with all early rumors, these should be taken with a grain of salt and AMD can certainly tweak some things before the launch but these information is what we have are hearing now. We will certainly keep our ear close to the ground as we are bound to have more info as we draw closer to the launch date.