As of the end of 2014 we have:
| Family | IsDefault | Version |
|---|---|---|
| 3 | False | WA-GUEST-OS-3.17_201407-01 |
| 3 | False | WA-GUEST-OS-3.20_201410-01 |
| 3 | True | WA-GUEST-OS-3.21_201411-01 |
| 4 | False | WA-GUEST-OS-4.10_201407-01 |
| 4 | False | WA-GUEST-OS-4.13_201410-01 |
| 4 | True | WA-GUEST-OS-4.14_201411-01 |
According to the documentation site (http://msdn.microsoft.com/en-us/library/azure/ee924680.aspx) the latest versions are due to expire on the 11th of January with the new versions being enabled on the 5th January. I guess that means a lot of people will have to spend their first week back at work testing the new os release in the 5 working days before the existing guest oses are retired.
Developer Rants 