It seems to me (just opinion) that one might reasonably leave these in
place until there is a clear path either to re-register using the new
IDN standards or, if it proves impossible to support any of them in
the new standard framework, to withdraw them on a reasonable time table.
That path is already completely clear and could have been implemented
a while ago. As for "withdrawing them on a reasonable time table",
how about "now"? The IDN testbeds are no different than the testbeds
for any other Internet standard.