HP posted a press release (opens in new tab) about some new PCs that will launch later this year, and one of them offers the AMD Radeon R9 380 -- which is a GPU that has not yet been announced.
Obviously, AMD has not released the AMD Radeon R9 380, so information about the GPU is practically non-existent. In fact, AMD has not even confirmed that the new GPU would be called the AMD Radeon R9 380, but we expect AMD to release its new series of GPUs sometime this year.
Despite the lack of information from AMD, HP's upcoming HP ENVY Tower can optionally come with either an Nvidia GeForce GTX 980 or an AMD Radeon R9 380.
Because the R9 380 is an option against the Nvidia GeForce GTX 980, it seems fairly safe to assume that the AMD Radeon R9 380 will be AMD's flagship GPU. We can't determine performance from this at all, of course.
It has been speculated for some time that AMD's flagship would be the AMD Radeon R9 390x, just as the AMD Radeon R9 290x is AMD's current flagship GPU. Although it presumably won't be the initial flagship GPU from AMD, it is possible that cards with the "x" nomenclature will launch later, perhaps as part of a mid-cycle refresh scheme.
According to the press release, these systems will be ready for "back to school" this year, which means we could see this GPU come out for sale before summer ends. So far, AMD and HP have not replied to our queries, but if companies like HP are starting to list systems with the new GPU, we expect to see its release to the public in the near future.
Update, 5/4/15, 2:30pm PT: In addition to the R9 380, two other GPUs were named for use inside of HP's new All-In-One systems. These GPUs, AMD Radeon R7 A330 and AMD Radeon R7 A360, have an "A" prefix that we haven't seen before. They are clearly listed as dedicated GPUs and can be used with Intel CPUs, so they aren't APUs. We have still received no comment from AMD.