Não é possível com a última versão do Skype, que deveria ter feito isso há muito tempo.
Você pode verificar seus :
We have recently introduced the ability to hide a Skype user’s IP address and we’ve set this as a default status in the latest versions of Skype.
Starting with this update to Skype and moving forward, your IP address will be kept hidden from Skype users. This measure will help prevent individuals from obtaining a Skype ID and resolving to an IP address.