Yes, you can use order parameter in GET Users query
http://quickblox.com/developers/Users#Sort
For example, you would like to sort users by last_request_at field:
https://api.quickblox.com/users.xml?order=asc%20date%20last_request_at
iOS SDK way:
NSMutableDictionary *filters = [NSMutableDictionary dictionary];
filters[@"order"] = @"desc date last_request_at";
// filters[@"filter[]"] = @"number id in 1,3,4";
[QBUsers usersWithExtendedRequest:filters delegate:self];