Basically if you already own the gear and have free or cheap electricity, then go ahead and get back into mining.

If you don't have the GPUs and your electricity is greater than 10 cents a KwH then you should hold off for now and see where the future takes us. You should also take into account the next Ethereum fork upgrade which will reduce the issuance to 2 ETH per block from 3 ETH per block, so there is another mining profit reduction right there.