if $399 price stands, will be the best gpu card your money can buy to mine anything. Where I live you can't find polaris for less than $320, so nobody is buying them. The best idea right now is wait for volta but that is in few months yet.
Waiting for voltra is a horrible idea, Your missing out on mining lots of coins while your waiting for voltra release, Too far into the future, most likely delays and gpu shortages,
More than likely coins will pump up hard after the bitcoin cools down. Look at Zen coin, monero, decred, etc all of the legit coins are up in value by 3x+ from their lows. If your always waiting for the next best hardware you'll be mining the coins with the latest hardware but they will be 10x more expensive and difficult to mine. Good luck waiting around on the sidelines. Time is money and that's way more important than waiting for the latest hardware.