We have been through a similar exercise recently. The problem is that there is no such thing as a standard set of test cases as every SAS site is different. However I'd suggest you create a list of the features that are important to you, I found it useful to group test cases into:
Accessibility - can you access a feature or tool?
Data Connectivity - can you connect to or access a data source?
Functionality - does your SAS application run successfully and does it produce the same results?
Performance - does your new SAS version perform at least as well as the previous version? Does it meet expectation?