Digital Media Designer have just published an article covering some of the new features we can expect from InDesign CS3 when it arrives in Spring 2007. As well as confirming Adobe have an early copy running on an Intel Mac, they cover some of the new capabilities.
Individual Element Transparency
You will be able to adjust the transparency of certain elements such as strokes and fills individually rather than just the whole object as in CS2.
InDesign can now apply effects to objects using a similar scheme to layer styles in Photoshop.
New Fitting Options
You now have the capability to assign a fitting option to boxes before import so pictures can be resized far quicker than the current manual process. This can be saved as a layer style as well.
You can import multiple instances of text and images at the same time and determine what is inserted where by cycling through them with the arrow keys.
You can see more of the article with screenshots here.