Thank you for your reply the friend.
It is already 2 weeks that I wait for my rx580 8go. But I think to cancel it to take 4go.
what do you think about it ?
No point in waiting for the 8 GB. The hashrate is almost the same after BIOS mod. I say get the 4GB. Cheaper, so ROI is quicker and the faster you start, the faster that will happen.