Static IP Address for Azure Cloud Service(Web Role)
Azure now supports reserving IP addresses: http://azure.microsoft.com/blog/2014/05/14/reserved-ip-addresses/
As long as you do not delete a deployment, but rather upgrade it, you will keep your "VIP" (Virtual IP address).
You also can deploy to a staging instance and "Swap VIP", which means moving your production VIP to your staging slot, and your staging VIP to your production slot. In effect, this moves your staging slot into production.
You cannot allocate an IP address permanently to a cloud service, however. They are permanent only within a deployment.
When you deploy your cloud service, the service is assigned an IP address. You can then update the deployment in several ways without losing your assigned IP address.
Take a look at this blog post which enumerates what you can do with in-place updates, while preserving your IP address.