I started compiling ideas for supporting COLLADA in Cesium - https://github.com/AnalyticalGraphicsInc/cesium/wiki/Models-Details. Also, see the discussion with the larger WebGL community - https://groups.google.com/forum/?fromgroups#!topic/webgl-dev-list/fS84N2KTjwA.
We’ll support COLLADA FX, COLLADA Animation, and interaction with CZML. We are thinking server-side convert COLLADA to JSON. Use the COLLADA Refinery and perhaps some custom conditioners to optimize the original model for rendering, e.g., generate shaders for common profile -> triangulate -> flatten hierarchy -> reduce texture sizes -> generate discrete LODs -> vertex cache optimize. Finally, use JSON.NET, XSLTJSON, or our own code, to convert to JSON. When the client receives the JSON, it almost has no processing to do, and can just render it. The JSON is not a full COLLADA spec; for example, the server will convert polygons to triangles, and generate shaders to support the COLLADA Common Profile.
There are lots of open questions. Take a look at the wiki, https://github.com/AnalyticalGraphicsInc/cesium/wiki/Imagery-Layers-Details, and let’s discuss.