The POW Ethereum that we mine today will stay with the current DAG. However if you want you can mine ETC right now which will work with your 4GB GPU. Unfortunately 3GB don’t work anymore on ETC since dag is exactly 3GB right now.
Nothing resets, it just like a fork in the road. On the left you get POS and no miners and on the right you continue the old chain like nothing happened.
What about the value? I bet it won't be the same, I remember what happened to BTC and Bitcoin Cash.