I'm like internet programmer think that
adding new TLD domain names with more then three letter can cause a problem of scripts.
For example the line of perl script: $email !~ /^.+\@(\[?)[a-zA-Z0-9\-\.]+\.([a-zA-Z]{2,3}|[0-9]{1,3})(\]?)$/
which
means that new TLDs won't be accepted by this script. And most people have this line
in their scripts, because it is a standard e-mail check. So this will cause a problem
of rewriting of scripts.