I don't think you need to worry about routers. They route packets between IP addresses, not DNS names. And the millions of lines of business logic will still be able to handle Latin characters, they're not going to break overnight. That's because the data entry fields for email names should already be filtering out non-Latin stuff (if it's not, they deserve everything they get).
Granted, they may need changes to allow non-Latin URLs to be entered but that's a management issue and vastly different to Y2K, where applications were expected to stop working.
Aside: most Y2K (financial) applications were fixed well in advance simply because they work with dates multiple years into the future anyway. For all the money a major telco spent on Y2K, we found one problem and that was a web page listing the date as Jan 1, 19100 (because some clown didn't realize that a tm_year
was number of years since 1900, not just the last two digits of the year).
I suspect this issue will have even less impact than Y2K.