I've filed a new connect item: Release Service Pack 3 for SQL Server 2008 R2

Maybe you want to vote?

Many organizations are going to stay on SQL Server 2008 R2 long after they fall out of mainstream support. Getting more of them on a final Service Pack rather than having them on one that is some years old, would save a lot of support costs.

SQL Server 2008 R2 should not go with a lot of released cumulative updates but without a final service pack.