Depends on our registrars and if they ever add support for .pk registrations. Honestly this is not a very popular domain extension to begin with (.com, .net, .org, .us and .co.uk are our most popular extensions), so it would need to grow in popularity / need before we would consider it, we will not add it just because, there really needs to be a market requirement for it here.
Now, anyone can register a .pk domain (or any other extension that we do not support) with another registrar and still host their domain with ASPnix by setting their domains name servers to ours.
Christopher York ASPnix Administration Team www.aspnix.com