Kwant 1.4.1 has been released recently. By now the new version should be available on all usual channels.
This maintenance release does not introduce any new functionality, but fixes some backwards compatibility issues that were introduced by 1.4.0.
Most notably, Kwant 1.4.1 is more tolerant to scripts that use the now deprecated "args" mechanism of passing parameters. For example, value functions may continue to accept *args or **kwargs as long as the new "params" parameter-passing mechanism is not used.
Please see the "what's new" document  for a detailed list of changes.