Microsoft has released SQL Server 2008 R2 Service Pack 2 Cumulative Update 4, which is Build 10.50.4270. I count 34 fixes in the public fix list. Some of these fixes look fairly important, so you should take a look at the fix list.
This Cumulative Update is only for SQL Server 2008 R2 Service Pack 2. It will not work with any other major version of SQL Server or with any other Service Pack Level.
If you are running SQL Server 2008 R2 Service Pack 2, you are on the latest branch of the SQL Server Server R2 “release tree”, which is a good place to be. This means you have a much longer time remaining before your Service Pack is retired.
When a SQL Server Service Pack is “retired” that means that it is considered an “unsupported service pack” by Microsoft CSS. This means that you will only get limited troubleshooting support until you upgrade to a supported Service Pack. It also means that there will be no more Cumulative Updates for that Service Pack.