You can edit the plugin manually (class-gfemailblacklist.php) to enable blocking wildcards until an update comes along.
After line 180 add:
$topLevel = '*.' . $this->gf_emailblacklist_clean( rgar( explode( '.', $domain ), count(explode( '.', $domain ))-1 ) );
Change line 196 from:
if ( ! in_array( $email, $blacklist, true ) && ! in_array( $domain, $blacklist, true ) ) {
to:
if ( ! in_array( $email, $blacklist, true ) && ! in_array( $domain, $blacklist, true ) && ! in_array($topLevel, $blacklist, true ) ) {
Wildcard domains should work as expected.