According to Mydrivers, the AMD RX 580 and RX 570 will face a small delay in release from their original planned time, due to the upcoming launch of Ryzen 5 on 17th of April, the day before.
This delay is purely market related and won’t bring us anything new with the optimization or architecture of the card over if it was released on the original April 4th date.
The RX 580 and RX570 will have a considerable boost in performance over the previous gen RX 480 and RX 470 cards but will feature the same memory amount 4 and 8 GB for the RX 580 and 4GB for the RX 570.
We will keep you updated as we get more news.