Hi,
We demo'd a sample at the Dev Summit last week which shows basic clustering functionality and can be implemented today using 10.2.7. Improved support for clustering is still on the roadmap for the Quartz release. But the sample may be enough for you to work with right now - it should perform adequately for 10s of thousands of graphics, but you should be cautious if you have 100s of thousands of graphics.
We're just wrapping up those demos and will post them on ArcGIS.com within the next couple of days.
Cheers
Mike