Basically if you got any 4GB GPUs you should sell them ASAP before they completely stop working under Linux and with the 8GB as GPU0. Because there is going to be a flood of them on eBay and Craiglist and it'll be tough to sell them.
What I did was basically sell some of my 4GB RX 470 for like $80 and bought 8GB variants for $100-125 USD. Currently its the only solution to the DAG problem. Plus when all 4GB stop working plus the ASICs the difficulty should be less and more profit for your 8GB GPUs.
Thanks by the answers guys, you are amazing.
I'll put them on sale this is the momento to take advantage of the GPU high prices (at least in my country) and wait for the prices of 8GB cards to decrease.
I'm keeping an eye on
5700 XT and
RX 580 prices.