AMD's next Radeon graphics card series has been the victim of much speculation, and predictions of when the first card comes out have been all over the board - you might as well throw a dart at a 12-month calendar and your guess will be as good as any.
That said, the folks over at VideoCardz have a source that says the first card will arrive next month. This information came about because one of the site's readers (supposedly) works at XFX, and provided paper proof that the Radeon R9 370 is in the system, ready to launch next month. Up to this point, I think this is the best hint we've seen.
It's interesting to note, though, that it's not just April, but "early April". It's also interesting because if the R9 370 launches first, it will be one of those rare times when a vendor releases a mid-range card ahead of a high-end one. That won't do too much to satiate the appetites of those who've been anxiously awaiting the 300 series to arrive - unless all they were intent on getting was a ~$200 model.
XFX's Radeon R9 270 Double Dissipation Edition
If AMD does in fact deliver an R9 370 in early April, it will follow NVIDIA's enormous GeForce GTX TITAN X, which is expected to launch alongside the company's GPU Technology Conference next week. Pricing is still not confirmed on those, but I think it's safe to say that it will match the fact that it'll be the fastest single-GPU solution on earth.