The problem is not with the user picker widget itself, but rather with the service used to fetch the suggested users. The user picker widget passes the limit as a request parameter, but the suggest service, uorgsuggest.vm hardcodes the limit to 10 here https://github.com/xwiki/xwiki-platform/blob/master/xwiki-platform-core/xwiki-platform-web/xwiki-platform-web-templates/src/main/resources/templates/uorgsuggest.vm#L48 . The fix is to read the limit from the request parameter, defaulting to 10 if no value is specified.
