Search non-conforming golf clubs and you'll see that it seems to be a non-issue.
Here's one typical comment: Old grooves never gave me an advantage so why would these...just more fun. Besides, I'd love to see the USGA ruffled as they are, in my opinion, a (mostly) buncha pompas asses anyhow. They are several little things, like ball details, that could be done instead of more costly equipment issues which cost more. As usual however, politics and red tape rule. Go Feel golf!
From another source: One major manufacturer estimated that 99-percent of all golfers will be unaffected by the new groove rules until 2024.