As usual, VideoCardz knows what this is about and leaked photos of five upcoming Radeon RX 570/580 series video cards from Sapphire. Pictured below is the Sapphire Nitro+ Radeon RX 580 Limited Edition. There's also a regular Nitro+, a RX 580 Pulse in 4GB and 8GB editions, and a compact-sized Pulse Radeon RX 570 Mini.
On a related note, there's some chatter about an upcoming NVIDIA event on April 29. The NVIDIA Italy page teases something is coming on that date. There's some speculation this could be a Shield product but given that this is only posted by NVIDIA Italy and doesn't use US-style date format it appears this is more of a local event rather than something big.