Instead of phasing out license plates from the same system and same design that has been around since 1986, Wisconsin is adding a seventh character to its license plates as of a few weeks ago. The combination will be three letters followed by four numbers.
When Iowa reset in 1997, all license plates got replaced with a new design and 000AAA character set. Then in 2012, we hit the limit and swapped the letter-number positions. Shortly thereafter, the DOT announced that all the 1997 issues, and then subsequent ones, would be replaced after a decade. (Right now, I think the replacements are somewhere in the N’s or maybe P’s.)
Wisconsin, however, hasn’t replaced anyone’s. It reversed letters to numbers in 2000 (meaning the first run-through lasted 14 years, a hair shorter than Iowa’s), and after another 16½ years hit the limit again. But since a plate issued in, say, 1988 as EKU279 could theoretically be in use today, there wasn’t anywhere to go but wedging in another digit. A little thinking ahead and database checking could have pre-emptively solved this issue, but, oops. Now America’s Dairyland will have the same design for the rest of the century or until the FIBs take over, whichever comes first.
CORRECTION 9/15/22: All pre-2000 plates were replaced starting in 2000, so the six-character series on the road today are from this century.