There was an announcement recently that Service Pack 3 for SQL Server 2008 R2 was released. This is the final SP for that version and is mostly a rollup of all the previous cumulative updates (CU), though there are a couple additional items included.
This is good news, and if you are running the "R2" version, I'd test this and install it. No more CUs will be released, though you'll want this SP installed in case additional security patches are released during extended support. The last thing you'll want is a crisis situation where you need to install a security patch based on SP3, and you haven't tested this update.
Earlier this year, Microsoft announced that we'd get one last SP for both SQL Server 2008 and 2008 R2. That was good news as many people are running these versions, and they haven't installed all the previous CUs. I can understand this situation, and it would be good to bundle all the changes together in one final patch for companies that find the platform suits their needs. It's also a fair request for customers that paid Microsoft for a platform and should receive all patches developed during its lifecycle. Including a final patch that closes out support.
I'm still waiting for an SP4 for SQL Server 2008 and I hope we get one soon. I'm not sure what the plans are for SQL Server 2012, 2014 and future releases, but I'd like to continue to see the bi-monthly CUs, an annual SP, and a final SP when each version transitions from mainstream to extended support.
UPDATE: SQL Server 2008 SP4 was released just after this was written. It is available here: http://www.microsoft.com/en-us/download/details.aspx?id=44278