The test is currently visible only to a "small percentage" of users who search for certain broader topics, such as home offices and abstract art. Whether or not it expands will likely depend on early results. With that said, it's hard to see Google turning down shoppable images. If you're already using a general image search to look for product ideas, you're that much more likely to tap an ad and make a purchase.
Pinterest is testing shoppable ads in image searches, potentially pitting it against Google and Instagram. The pilot is currently limited to sponsored ads and is available to a "small percentage" of users carrying out broad-based searches. Analysts said expansion of the tool would depend on preliminary results.