Quick Convert Image to Grayscale Non-Destructively in Illustrator

There is a way in Adobe Illustrator to quick and easy convert images to grayscale non-destructively using Rasterize effect from Effect menu. All you have to do is to select your image (or Layer if you have multiple iimages on the same layer) and to use effect from Effect > Rasterize..

In Rasterize dialog choose Grayscale from Color Mode drop-down list, specify resolution (choose 72 for faster rendering). You can even add white border around image, click to select White radio button in Background section and specify width in Add __ Around Object section.

Rasterize dialog in Adobe Illustrator

You can always change settings or to remove this effect from APPEARANCE panel.

Bibliography:
Real World Adobe Illustrator CS5

Reference:
Illustrator / Working with effects

Product used in this tutorial: Adobe Illustrator CS5